The fact that auras from Diablo 2 items stack per item always kind of makes sense, but then you get that aura level per item, a pretty simple little test here to show you how it works.

Diablo 2 Resurrected Holy Fire Damage - Aura Bug Triples Your Damage On Diablo 2 Resurrected Aura Paladin! 

Diablo 2 Resurrected Holy fire 

Quick History of D2R Changes

When Diablo 2 resurrected came out, and they inevitably released the first patch, they made a pretty big change to how Holy Fire holy shock and holy freeze auras were going to work, the biggest thing was that it was going to increase your damage based on how close to the monster that you were if you're looking at this tool tip, a level 3 Holy Fire, actually only adds two to five fire radial damage, the damage that ticks in the area around you, but what the tooltip.

Now shows you the maximum damage that it will do, if you are at minimum range to the monster, if you're literally right on top of the monster, you're actually gonna be able to do maximum damage of 10 damage, if you were to roll maximum damage every single time,  now if you remember when they first released this all of a sudden, you had like dual Dragon handed Justice paladins, Just charging around killing high-level cows and it was ridiculous right, everybody was up in arms, they nerfed it.

Then they buffed it again, and while they landed somewhere in the middle with the synergy they left that damage component, and if you're at the minimum distance, you're gonna get double the radial damage, now before talking about what the bug is and this bug has existed since LOD and again.

Diablo 2 Resurrected Holy fire - What the desired impact was?

If you were using one of these holy damaged auras, it was giving you some AOE damage clear for what was basically a melee build, you would use this with the Zeal or Dani and add some Elemental damage to your attack, but the AOE pulse was supposed to help butter up monsters before you had to come hit them, effectively giving you AOE damage.

Diablo 2 Resurrected Holy fire - Holt Fire Skill Test 1

Now here's the problem, this is normal difficulty on player eight, go find a zombie and show you how long it takes to kill them, hopefully rolling Max damage every time, but just keep in mind, between 2 and 10 damage per tick when the aura up alright, some zombies here again. Around players 8 difficulty means that these zombies have on average 40 hit points, just going to walk up, turn on Holy Fire, and minimum range.

Holy Fire or up one tick two tick, they're gonna heal a little bit while this happens three ticks, four ticks, five ticks, six seven, basically seven right, they're gonna be healing while it happens for those,  basically seven ticks, if doing between two and ten damage at minimum range to the monster that means that on average.

Diablo 2 Resurrected Holy fire - Item Stacking Auras

How stacking an aura on an Diablo 2 item is supposed to work? 

What you're looking at is a Hand of Justice a dragon, that drastically modified these Diablo 2 items, all they have are the base Rune stats that they normally have, just took the level one Holy Fire and reduced it all the way down to level one, just to be able to do this test to try to minimize variables.

If you look at it, take this armor, put on a level one Holy Fire ore, and how much fire damage gain on 2-7, gain 6 to 18 damage and that follows up with what a level one Holy Fire ore should give us. Now put on the Dragon shield, what a level two holy fire damage supposed to add to a melee hit, at level two,  gaining 9 to 24, so that should put you at 11 to 29, 

Diablo 2 Resurrected Holy fire - Why do it without a weapon? 

Obviously, the weapon also has damage on it, and then a bunch of points into the stats, but when put on a level three, the fire damage that gain is at 12 to 30. 

Here's the problem when you stack these auras, the radial damage should also be a level 3 holy fires radial damage, so looking at the skill, it should be doing 2-10 damage, so that's 10 at maximum.

If against the monster, just like the skill set, so one level one, it should add the aura levels together, and then apply them as a single Source.

Diablo 2 Resurrected Holy fire - Holy Fire Item Test 2

What if roll Max damage every single time, you know 10 would be the maximum damage from the skill level times three, so that would be 30 damage.

Look at what the minimum life of a zombie would be on players eight,  so if a base zombie is in normal difficulty and the blood more rolls between 7 to 12 hit points and player eight difficulties will take your base life multiplied by 4.5 the minimum life, a zombie can have on players 8 difficulty is 31.5 hit points, even if you round down the minimum life a zombie could have is 31 hit points, so if maximum damage from a level 3 holy fire even at zero Radius, so maximum damage gets the full double effect in three ticks.

Diablo 2 Resurrected Holy fire - Explaining the Bug

There's a whole history of bugs from elegy that so just keep in mind, like Aura stacking with your mercenary where you can swap gear and get infinite stacks of an aura, and then walk outside in one-shot stuff.

Looking at specifically this part about how Aura stacking Works in a known bug that was in LOD furthermore when multiple items supplying the same Aura are equipped, not only is the aura level supplied at the combined total, but the radial damage of the aura is supplied at that combined level total per item equipped.

In a little bit easier layman's terms when you equip multiple Diablo 2 resurrected items that apply either holy freeze Holy Fire or holy lightning, you add the levels together, so this would be a level 3 Holy Fire Aura, and then the radial damage component, so the AOE damage component on the skill is applied at level 3 in example per item equipped, since three items, all supply a level one Holy Fire aura that is a level 3 Holy Fire auras radial damage applied for one two three times the amount of damage when thinking about it that way, the maximum damage that could output from this at level 3, Holy Fire would be 30 damage per Tech and in that zombie that just killed if you watched how much damage. 

While it took three ticks to kill him, they were basically dead after the second one, if doing the average damage of this new equation right, so a maximum of 10 radial damage per item equipped being 30 with a minimum damage being 2 4 to 30 is 17, 17 damage in three ticks will kill your average zombie every single time three ticks would be doing 51 damage on average, so since only barely needed the third tick to kill this zombie seems pretty conclusive that not only are you getting the combined level of the Holy Fire Aura, but radial damage is being applied per item that throws on went and tested with just two items.