One of the most important goals within Diablo III, or any ARPG for that sake, is to become strong enough to take down every enemy on your road. However, the in-game tooltips in Diablo III do not explicitly state how damage is calculated, what types of multipliers exist and how it all comes together for you to damage a target... or hordes of targets.
In this guide, we are going to explain damage calculations and multipliers while answering common questions that you see roaming within the community like: How does the Weapon Damage Range define damage of abilities? What is the difference between additive and multiplicative multipliers? All these questions, and many more, will be answered here: Stay awhile and listen!
The base of every damage calculation in Diablo III comes from your Damage Range (or from Thorns in some cases), which comes mainly from your Weapon(s) and eventually Offhands (Source, Mojo, Phylactery) or Jewelry (Rings and Amulet). Let's take a simple Level 1 Weapon as example:
On our unsocketed Weapon, we can see that it has a range of 2-3 damage, meaning this weapon has 2 Minimum Damage and 3 Maximum Damage. These rolls are the implicit range rolls of the "Level 1 Wand Weapon Base": any item of the same weapon base, regardless of its rarity and primary affixes, will at a bare minimum have this damage range. On the second weapon we can see that it has a damage range of 272-273, meaning that Flawless Royal Ruby grants +270 Minimum Damage and +270 Maximum Damage to the base.
Note that the primary affix "+X% Damage" on Weapons increases both minimum and maximum damage ranges of the Weapon. Other sources of damage range such as Jewelry or Offhands are applied on the damage range only after the +X% Damage Weapon Affix. In order to get our average damage, we need to divide by 2 the sum of our minimum and maximum damage range:
Thus, we can calculate our socketed Wand average damage, which should be (272 + 273 / 2) = 272.5 average damage per hit. In order to get our Weapon Damage Per Second (DPS), we need to multiply the average damage by the Weapon Attack Speed which is 1.2 in our case: this brings us to a grand total of 272.5 * 1.2 = 327 DPS. For more information about Attack Speed and Breakpoints, check out this article written by Northwar!
Thorns damage does not take Weapon damage into consideration. This means all sources of average damage (Weapon, Rings, Amulet and Offhand) are useless for Thorns builds.
All damage done by Thorns is Physical. Demon's Skin(2) Bonus, Demon's Hide(2) Bonus and Asheara's Uniform(3) Bonus are the only exceptions as they respectively grant Fire Thorns and Holy Thorns.
Thorns damage cannot critically strike (except with Envious Blade).
Rolls on Shoulders, Chest, Amulet & Belt: 5334-7696 Thorns (7697-9500 for Ancients).
Rolls on Rings, Helmet, Bracers, Gloves, Pants, Boots & Offhand: 2401-2880 Thorns (2881-3500 for Ancients).
Nailbiter & Neanderthal: 5334-7696 Thorns (7697-9500 for Ancients).
Heart of Iron: 300% of your Vitality as Thorns.
Boyarsky's Chip: 16,000 Thorns, up to 136,000 at level 150.
Flawless Royal Topaz in Weapon: 38,000 Thorns.
Note that the character sheet tooltip states that Thorns damage is increased by a portion of your Primary Attribute: this is an heirloom from early Diablo III, when Thorns damage was only increased by 25% of your Primary Attribute. This is however not the case anymore, you do benefit from all your Primary Attribute!
As seen earlier, in regard to Thorns damage calculation, your average damage is replaced by your Thorns value. This value is defined by your sheet Thorns amount, which is directly buffed (and shown in your character sheet) by the following effects:
Thorns of the Invoker(2) Bonus + Iron Skin Reflective Skin
Tough as Nails
Spear of Jairo
We call these buffs Thorns Multipliers. Every one of these bonuses is a separate multiplier to your Thorns amount, the only exception being Thorns of the Invoker(2) Bonus, which is additive with Iron Skin Reflective Skin. We can also mention Aberrant Animator which is a passive that gives 200% of the Necromancer's final Thorns amount (after all Thorns multipliers have been applied) to its minions.
But there is more to it! Thorns are divided into 2 categories that we will call Real Thorns and Converted Thorns for convenience.
The first thing to know is that Real Thorns damage is calculated using only your Thorns amount and all your damage multipliers. The second thing is that in a normal scenario, whether it is a buff or a debuff, all additive damage buffs stack additively within their category and their sum forms one separate damage multiplier (see below). This is however not the case with Real Thorns as buffs and debuffs from the additive category are multiplying with each other, meaning they're both separate damage multipliers for this Thorns category. Real Thorns sources are:
Thorns applied when a monster hit you (or your minions with Aberrant Animator).
Thorns applied by Hack.
Thorns applied by Thorns of the Invoker(2) Bonus.
Another thing to bear in mind is that Vo'Toyias Spiker is a 100% additive damage debuff working for the whole party but only for Real Thorns and not for Converted Thorns. This means it stacks additively with other additive damage debuffs like Strongarm Bracers but on the other hand, as seen above, additive damage buffs are multiplying with additive damage debuffs.
Also, Reflected Thorns and Hack cannot proc Area Damage. On the other hand, AoE Thorns from Thorns of the Invoker(2) Bonus can proc Area Damage. Thorns from Hack are applied in a 15 yard radius and can proc Area Damage as well when combined with Thorns of the Invoker(2) Bonus.
Converted Thorns follow normal damage calculation rules. The reason is that they are using your Thorns amount as base damage but unlike Real Thorns, they have a "Skill Damage" Multiplier. Sources of Converted Thorns are the following:
Thorns applied by Sanguinary Vambraces
Bombardment Barrels of Spikes
Consecration Bed of Nails
Steed Charge Spiked Barding
Thorns of the Invoker(6) Bonus
For this Thorns category, additive buffs and debuffs stay additive with each other and as seen above, Vo'Toyias Spiker additive damage debuff does not work.
Every skill in Diablo III deals a specific amount of Weapon Damage, also called Skill Damage Multiplier. If we look at Magic Missile, we can see that the skill without rune deals 230% of our Weapon Damage. This means that to get our average hit with an unruned Magic Missile, we need to multiply our average weapon damage by this skill multiplier:
In practice with our average damage defined in the section above and an unruned Magic Missile dealing 230% of our weapon damage, we should deal on average 626.75 damage per hit:
Then we need to add all our damage multipliers to get a final damage value. Note that some skills have a special Weapon Damage scaling: Seismic Slam Rumble, Ancient Spear Boulder Toss and Meteor Star Pact have a base Weapon Damage value and consume all remaining resource after the initial skill cost to add Weapon Damage to the base value. Skeletal Mage Singularity has a similar scaling but the remaining resource is scaling a separate damage multiplier to the Skeletal Mage instead of scaling its base Weapon Skill Damage. This means Maximum Resource and Resource Cost Reduction give a slight damage increase for those skills.
Now that we defined our base damage, we can now dive safely into more thorough damage calculations. The main idea to keep in mind is that pretty much everything in Diablo III acts as a damage multiplier to your base Weapon Damage (or Thorns Value in some cases).
By definition, buffs are beneficial effects and by opposition debuffs are harmful effects. In Diablo III, when we speak about buffs, we mean beneficial effects applied on players while debuffs are harmful effects applied on monsters (hence also beneficial to players). That being said, practical differences between buffs and debuffs are anecdotic in Diablo III when it comes to damage calculation, only affecting the Additive Damage category in a few cases.
The main rule is that every damage buff is additive with others buffs in its own category, and these categories then multiply your damage. Sadly, there is no absolute rule of thumb to tell how every damage buff is working: you just have to know. Luckily for you, we are here to nail it and explain to you how all these damage buffs and multipliers work together!
Primary Attribute is Strength for Crusaders and Barbarians, Dexterity for Monks and Demon Hunters and Intelligence for Wizards, Witch Doctors and Necromancers.
This affix is easily found on every piece of gear and one can get plenty from Paragon Points (which is the sole reason to grind Paragon after hitting Paragon 800). A naked level 70 character by default has 217 of its Primary Attribute. The Primary Attribute acts as a damage multiplier to your base weapon damage:
Taking the example above, we can now define our unruned Magic Missile damage as 1986.79 average damage per hit:
There are only a few Primary Attribute Multipliers existing in the game:
Witch Doctor Gruesome Feast Soul Harvest
Critical Hit Chance & Damage
Critical Hit Chance and Critical Hit Damage are affixes that simply say "You have X% chance to deal Y% more damage with every hit" with X being your Critical Hit Chance and Y being your Critical Hit Damage. This means these stats act just like any other damage multiplier in Diablo III:
Using your Critical Hit Chance and Damage as a damage multiplier will only give you your average hit, do not include it if you want to find out your average non-critical hit or set your Critical Hit Chance at 100% if you intend to calculate your average critical hit.
However, this formula becomes part of the normal damage calculation when it comes to DoT damage like Rend or Haunt, in order to avoid critical chance RNG and critical hit snapshots. Yet, crit debuffs (applied on monsters) such as Iceblink, Multishot Wind Chill or Corpse Lance Brittle Touch are not taken into consideration for the damage calculation of these skills.
Some setups like LoD Twister Wizard can be built around Shi Mizu's Haori to get 100% Critical Hit Chance at all times, generally by using shield mechanics such as Galvanizing Ward or Fortress Ballista. It is worth mentioning that some Weapons come with a special 31-35% Critical Hit Damage Affix roll: Exarian, Rabid Strike and Starmetal Kukri. The Witching Hour is also a Belt of choice for its 26-50% Critical Hit Damage roll, combined with a 5-7% Attack Speed roll.
Elemental Damage is a separate damage multiplier that increases the damage of skills depending on their element, which generally depends on the rune chosen. This damage roll, that reads "Arcane / Cold / Fire / Lightning / Holy / Physical / Poison skills deal X% more damage", is generally found on Bracers and Amulets, even though you can find it on some other items as a special roll (Stone of Jordan for instance). Elemental Damage rolls are additive with each other with their sum acting as a separate damage multiplier.
Mask of Jeram is a specific case that gives 150-200% Pet Damage. Pet damage from this legendary effect is additive with Elemental Damage but it is however not shown in your character sheet as it only applies to Pets. Black Hole Absolute Zero and Spectral Blade Flame Blades damage buffs from the Wizard are also additive with Elemental Damage.
Frostburn gives 20% Cold Damage as Elemental Damage but it has a special interaction with most Pets that makes them double dip this legendary effect, granting them 40% Cold Damage instead. Stone of Jordan has an interesting legendary affix that makes all your Elemental Damage bonuses equal to your highest one.
Here is a list of all the sources of Elemental Damage besides the normal 15-20% rolls on Amulets and Bracers:
Black Hole Absolute Zero
Spectral Blade Flame Blades
Akanesh, the Herald of Righteousness
Blackthorne's Jousting Mail
Gesture of Orpheus
Mask of Jeram
Stone of Jordan
Swamp Land Waders
The Burning Axe of Sankis
Won Khim Lau
Wrath of the Bone King
Elite Damage is a separate damage multiplier that increases the damage dealt to Elites. Elites include Champions, Rare Minions, Rare Elites, Bosses and Goblins. Note that other Players are also affected by Elite Damage.
This primary affix (except on The Furnace), that reads "Increases damage against Elites by X%" is very rare and generally found on Weapons and Offhands (5-8% range). It is however a guaranteed roll on Empyrean Messenger. Elite Damage rolls are additive with each other with their sum acting as a separate damage multiplier.
Stone of Jordan
Aughild's Authority(3) Bonus
Blackthorne's Battlegear(2) Bonus
Monster Type Damage
This category is pretty much unused in most builds in the modern Diablo III because you generally always have a better option. You can find those affixes as Secondary Affix on some legendary items and they are not shown in your character sheet. Similarly to Elite Damage, these affixes buff all your damage against specific monster types. Here are some examples:
Demon's Hide(4) Bonus
This category is probably the most complicated one for any Diablo III player. The name "Additive" can be misleading as it implies this category does not multiply your damage. This is misleading: the term additive is commonly used because in this category, you can find most of the damage buffs coming from your skills (hence why the name DIBS can sometimes be used as well) and as seen earlier, all damage buffs within the same category are additive with each other to form one separate damage multiplier.
This category includes for instance Taeguk, Gem of Efficacious Toxin (stacks), Hexing Pants of Mr. Yan or more generally, primary affixes on your equipment that increases the damage of a specific skill (worded as "Increases X Damage by Y%"). You can find Primary Skills Increased Damage Affixes on Belt and Pants, while Secondary Skills are spread on Helm and Boots for some, and on Shoulders and Chest for the rest. Offhands can roll any specific skill damage increase. However there are quite some special specific skills damage increases you can find like Voo's Juicer or Inna's Reach.
Buffs are applied on players. Global additive buffs are shown in your character sheet under the label "Damage Increased by Skills" while Skill Specific increases have their specific label and both are additive with each other. Debuffs are not shown in your character sheet as they are directly applied on monsters, hence calculated upon hit for every monster individually.
As a result, this category is more often than not "overloaded", mainly in group play (150% from Odyssey's End, 50% from Threatening Shout Falter + Horde of the Ninety Savages(2) Bonus, stacking Strongarm Bracers buffs). Even in solo play, some builds stack a lot of additive damage buffs such as Wizards (with Black Hole Spellsteal) or LoD Rapid Fire Demon Hunters due to Wojahnni Assaulter's 3,000% damage buff being additive damage.
This means adding more buffs to this category will generally result in a much lower relative damage increase than adding another separate damage multiplier buff. Skill Specific damage increases for Pets on your equipment do not follow this rule, they are a separate damage multiplier as explained in the section just below. But there's also some more specific rules applying to that additive damage category:
Buffs Snapshot Some skills snapshot damage buffs upon cast. Meanwhile this is not something one can notice with most skills, you will stumble onto that rule as soon as you play a DoT effect (Haunt, Exploding Palm, Rend) or a skill with a duration (Energy Twister, Spirit Barrage Phantasm, Bombardment). But channeling skills like Rapid Fire and pets like Hydras for instance do not snapshot damage buffs. On the other hand, debuffs are always fully dynamic as they are directly applied on the monster, they are only calculated when the monster is hit.
Thorns Interaction Buffs and debuffs are separate categories when it comes to Thorns Damage calculation. What we saw above is that whether it is a buff or a debuff, all damage buffs are stacking additively within their category and their sum forms one separate damage multiplier. This is however not true in regards to Thorns: buffs and debuffs from the additive category are multiplying with each other, meaning they're both separate damage multipliers for Thorns.
Yet, this is only true for "Real" Thorns such as Reflected Thorns or Thorns applied by Hack. Indeed, Converted Thorns such as Bombardment Barrels of Spikes or Thorns of the Invoker(6) Bonus are not affected, additive buffs and debuffs from this category stays additive with each other, as Converted Thorns damage are using normal damage calculations.
Pets Skill Damage
On your equipment, you can sometimes find primary affixes that increase the damage of a specific skill (worded as "Increases X Damage by Y%"). As seen earlier, in most cases, these are in the "Additive" Damage category. But when this affix buffs the damage of a Pet skill, they become a separate damage multiplier. Some special cases:
Fetish Army Damage is a separate multiplier for all your Fetishes, Fetish Sycophants included.
Poison Dart Damage is a separate multiplier for your Fetishes' Darts when using Carnevil.
Spirit Barrage Damage is a separate multiplier only for the Phantasm rune.
Even though Attack Speed scales the rate of attacks using Breakpoints in most scenarios, there are a few exceptions as is tradition in Diablo III. Wave of Destruction damage from Chantodo's Resolve scales with Attack Speed as a separate damage multiplier but with a reduced scaling of APS/1.75. Tempest Rush does not have Breakpoints but instead a static tickrate of 0.2 seconds and utilizes Attack Speed as a separate damage multiplier as well.
For most Pets, your sheet Attack Speed acts as a separate damage multiplier instead of scaling their own Attack Rate. This means Tasker and Theo is the only way to scale the Attack Speed Rate of most Pets. The only exceptions to that are Hydra and Command Skeletons, which use Breakpoints and scale their Attack Speed Rate off of your sheet Attack Speed instead of using it as a damage multiplier.
Yet, every Pet follows different rules. Mirror Images for instance do not use your Attack Speed as a separate multiplier and Attack Speed buffs (Slow Time Stretch Time or Laws of Valor) do buff their Attack Rate. Also, Spirit Barrage Phantasm is worth mentioning, as it is considered a Pet regarding Attack Speed, using it as a separate damage multiplier.
Attack Speed "double dips" with Carnevil + Fetishes because due to these items and skills in combination, Fetishes shoot Poison Dart when you do, which means they scale with your own Attack Speed Rate on top of using it as a separate damage multiplier. This is however not the case for Sentry with Embodiment of the Marauder(4) Bonus, as Attack Speed is not a separate multiplier for Sentries.
Other Damage Multipliers
If it doesn't belong to any other category, then it probably belongs here. Every other damage multiplier is its own category and they are fully dynamic (for instance Oculus Ring or Convention of Elements), which means you need to have them when your skill is hitting. They are not shown in your character sheet.
As a rule of thumb, all stacks of the same damage buff are additive with each other, their sum being a separate damage multiplier. Yet, as always in Diablo III, this is not an absolute rule, so here are a few generic examples and noteworthy cases:
Focus&Restraint both grant a 50% separate damage multiplier, for a total of 125% (1.5 * 1.5).
Oculus Ring gives a 85% separate damage multiplier that does not stack.
Mantle of Channeling grants a 25% separate damage multiplier when you're channeling some skills.
Archon and The Swami stacks are additive with each other.
Class by Class Overview
If the categorization and all the exceptions to every rule in the section above scared you, don't worry, we got your back! Below, you can find the explanation for most of the damage interactions class by class:
Spectral Blade Flame Blades as well as Black Hole Absolute Zero grant elemental damage buffs.
Energy Twister Gale Force and Disintegrate Intensify apply 15% additive damage debuffs for specific element damage (Fire and Arcane respectively).
Elemental Exposure gives up to 4 stacks of 5% damage (one for each element), their sum being a separate damage multiplier. Primordial Soul buffs this bonus to 10% per stack.
"Increases Hydra Damage" primary affix is a separate damage multiplier but remember that unlike other Pets, Attack Speed is not as Hydras use your sheet Attack Speed to scale their attack rate instead.
Archon grants a 30% global separate damage multiplier. Archon's stacks give 6% damage, additive with each other and with The Swami stacks, their sum being a global separate damage multiplier.
Vyr's Amazing Arcana(6) Bonus buffs each stack to 100% damage. Improved Archon is a 50% separate multiplier for Archon Abilities and Chantodo's Resolve Wave of Destruction. Chantodo's Resolve's Wave of Destruction damage scales using your sheet Attack Speed as a separate damage multiplier with a reduced scaling of APS/1.75.
Black Hole Spellsteal
Energy Twister Gale Force
Frost Nova Bone Chill
Slow Time Time Warp
Wave of Force Arcane Attunement
Fragment of Destiny
Orb of Infinite Depth
The Grand Vizier
The Twisted Sword
Wand of Woh
Delsere's Magnum Opus(6) Bonus
Firebird's Finery(6) Bonus
Tal Rasha's Elements(6) Bonus
The Typhon's Veil(6) Bonus
Vyr's Amazing Arcana(6) Bonus
The Barbarian is a staple for any group as zBarb, giving the group some powerful buffs.
Threatening Shout Falter applies a 25% additive damage debuff that does not stack. This debuff goes up to an outrageous 50% in combination with Horde of the Ninety Savages(2) Bonus.
Battle Rage gives 10% additive damage buff up to 15% with Marauder's Rage. Horde of the Ninety Savages(2) Bonus doubles that buff.
Cleave Gathering Storm
Threatening Shout Falter
Wrath of the Berserker Insanity
Blade of the Tribes
Blade of the Warlord
Bracers of Destruction
Bracers of the First Men
Fury of the Vanished Peak
Girdle of Giants
The Gavel of Judgment
The Three Hundredth Spear
The Undisputed Champion
Horde of the Ninety Savages(6) Bonus
Immortal King's Call(6) Bonus
Might of the Earth(6) Bonus
The Legacy of Raekor(4) Bonus
The Legacy of Raekor(6) Bonus
Wrath of the Wastes(2) Bonus
Wrath of the Wastes(4) Bonus
Wrath of the Wastes(6) Bonus
Necromancer does not have a lot of damage buffs but it does have powerful Critical Hit Chance debuffs (Corpse Lance Brittle Touch and Command Golem Ice Golem) and takes advantage of it in the zNecromancer support build.
Skeletal Mage Singularity scales with additional Resource spent, but unlike Meteor Star Pact and Ancient Spear Boulder Toss, is not additive with the Weapon Skill Damage but a separate damage multiplier instead. "Increases Skeletal Mage Damage" primary affix is a separate damage multiplier.
Simulacrums are not considered Pets! Hence they're not using your sheet Attack Speed as a damage multiplier and do not benefit from Enforcer.
Frailty Scent of Blood
Bonds of C'Lena
Gelmindor's Marrow Guards
Grasps of Essence
Maltorius' Petrified Spike
Mask of Scarlet Death
Nayr's Black Death
Scythe of the Cycle
Trag'Oul's Corroded Fang
Bones of Rathma(6) Bonus
Grace of Inarius(2) Bonus
Grace of Inarius(6) Bonus
Pestilence Master's Shroud(6) Bonus
Trag'Oul's Avatar(6) Bonus
Odyssey's End applies an insane 150% additive damage debuff (which can stack with several Demon Hunters) to enemies affected by Entangling Shot.
"Increases Sentry Damage" primary affix is a separate damage multiplier. Embodiment of the Marauder(4) Bonus 400% buff is a separate damage multiplier. Even with this bonus, "Increases Hatred Spender Damage" primary affixes stay additive damage buffs.
Marked for Death
Companion Wolf Companion
Cull the Weak
Dead Man's Legacy
Holy Point Shot
Leonine Bow of Hashir
Lord Greenstone's Fan
Sword of Ill Will
The Ninth Cirri Satchel
Embodiment of the Marauder(4) Bonus
Embodiment of the Marauder(6) Bonus
Gears of Dreadlands(2) Bonus
Gears of Dreadlands(6) Bonus
The Shadow's Mantle(2) Bonus
Unhallowed Essence(4) Bonus
Unhallowed Essence(6) Bonus
Hex Jinx offers a 15% additive damage debuff. Toad of Hugeness debuff is additive as well and can be stacked.
Mask of Jeram gives 200% Pet damage as an elemental damage buff.
Gruesome Feast gives up to 50% Intelligence as a Primary Attribute multiplier. This is additive with the 15% from Soul Harvest (30% with Sacred Harvester).
Spirit Barrage Phantasm uses Attack Speed as a separate damage multiplier like Pets. Similarly, "Increases Spirit Barrage Damage" primary affix is a separate damage multiplier for Phantasms. Frostburn legendary effect is double dipped by Phantasm, for a total of 40% Cold damage.
"Increases Fetish Army Damage" primary affix is a separate damage multiplier for all Fetishes, Fetish Sycophants included.
With Carnevil equipped, "Increases Poison Dart Damage" primary affix is a separate damage multiplier for Darts shot by Fetishes, but stay an additive damage buff for your own Poison Darts.
Big Bad Voodoo Slam Dance
Sacrifice Provoke the Pack
Pierce the Veil
Hex Jinx&Toad of Hugeness
Haunt Poisoned Spirit
Bakuli Jungle Wraps
Staff of Chiroptera
Swamp Land Waders
The Dagger of Darts
Ring of Emptiness
The Short Man's Finger
The Tall Man's Finger
Helltooth Harness(6) Bonus
Mundunugu's Regalia(6) Bonus
Spirit of Arachyr(6) Bonus
Zunimassa's Haunt(6) Bonus
Unity is giving you 5% additive damage buff for each nearby ally up to 20%, and 5% to allies.
Tempest Rush has a fixed 0.2 second tickrate and uses your sheet Attack Speed as a separate damage multiplier.
Rabid Strike'sMimic is a Mystic Ally in regard to the Bindings of the Lesser Gods legendary effect. Enforcer's separate damage multiplier does work on them but "Increases Mystic Ally Damage" primary affix does not work. Frostburn legendary effect is double dipped by Rabid Strike'sMimic if you use a Cold skill, for a total of 40% Cold damage.
Blinding Flash Faith in the Light
Breath of Heaven Blazing Wrath
Deadly Reach Foresight
Mystic Ally Fire Ally
Way of the Hundred Fists Assimilation
Crippling Wave Breaking Wave
Exploding Palm The Flesh is Weak
Mantra of Conviction
Bindings of the Lesser Gods
Incense Torch of the Grand Temple
The Fist of Az'Turrasq
The Flow of Eternity
Won Khim Lau
Inna's Mantra(6) Bonus
Monkey King's Garb(6) Bonus
Patterns of Justice(6) Bonus
Raiment of a Thousand Storms(2) Bonus
Raiment of a Thousand Storms(6) Bonus
Uliana's Stratagem(6) Bonus
Aegis of Valor(2) Bonus used to be the only stacking damage buff in the game whose stacks are multiplicative with each other for Heaven's Fury damage but got nerfed to the usual additive stacks behavior with Season 24 patch.
Vo'Toyias Spiker is a 100% additive damage debuff working for the whole party but only for "Real" Thorns. Those are Reflected Thorns, Hack and Thorns of the Invoker(2) Bonus. Converted Thorns such as Thorns of the Invoker(6) Bonus or Bombardment Barrels of Spikes are not affected.
Heavenly Strength gives a negative 20% additive damage, effectively making your other additive buffs stronger.
Shield of Fury and Hammer Jammers do not buff Area Damage ticks. Hammer Jammers proc from Knockbacks as well despite the tooltip. Bracer of Fury requires the target to be Blinded, Immobilized or Stunned when the hit happens.
Shield Glare Divine Verdict
Blade of Prophecy
Fate of the Fell
The Mortal Drama
Guard of Johanna
Shield of Fury
Belt of the Trove
Khassett's Cord of Righteousness
Warhelm of Kassar
Bracer of Fury
Norvald's Fervor(2) Bonus
Armor of Akkhan(6) Bonus
Aegis of Valor(2) Bonus
Aegis of Valor(6) Bonus
Roland's Legacy(4) Bonus
Seeker of the Light(6) Bonus
I hope this guide gave you all the insides about how the damage instances are processed within Diablo III! While damage interactions can be complicated with a lot of exceptions to mention, a good understanding of damage scaling mechanics and damage multipliers will make you a lot more insightful regarding optimisation and gearing choices, allowing you to maximize your Greater Rift pushing potential. Good luck!