Negation and Shadowclad WAI?

quickfoot

I tested a r12 Negation and an r13 Shadowclad on Preview the other day. They do now "buff" damage resistance past 50%, but I am not sure if it's WAI or possibly a bug.

Expected behavior: Enchantments to perform as tooltips suggest.
Noticed behavior: Enchantments buff damage resistance by about half as much as tooltips suggest.

"The damage resistance calculation of Negation and Shadowclad Enhancements has been updated. These should now be a little more effective." - Patch notes for June 4.

A r12 Negation says that it buffs Damage Resistance by 1.2% per stack, but instead of being an additive buff, each stack is multiplicative, so with 50% DR from Defense, 1.2% applied to that multiplicatively is effectively a 0.6% buff to DR.

(1- 0.5) * (1- 0.012) = 0.494

(0.5 - 0.494) * 100% = 0.006 * 100% = 0.6%

each additional stack becomes less effective than the one before it due to the multiplicative way the buff is being applied.

In short, each stack from these enchantments is a post-mitigated buff. I don't know if this was intended, but it makes the tooltips misleading.

What I would expect from reading the tooltips, is that each stack is applied additively to Damage Resistance, which would make the enchantments actually behave as the tooltips describe.

ie something like

DR = DR + sum(buffs)

I think this would be called "pre-mitigated" buff.

I'll post some data later, but for now, to reproduce the data, slot a negation or shadowclad enchantment, log enemies attacking you, and observe the effectiveness of their attacks chronologically.

quickfoot

Test done today on Live. First is Shadowclad, second is negation.

Shadowclad slotted, defense capped:


Let mob attack me and log data:


Results:



The first attack has no buff, so 50% effectiveness, 50% DR from defense, no deflect, no debuffs
Effectiveness = 100% * (1- 0.5) = 50%

The 2nd attack has 1 stack of shadowclad buff (4% according to tooltip), 50% DR from defense, no deflect, no debuffs
Effectiveness = 100% * (1- 0.5) * (1 - 0.04) = 48%

That's a 2% difference of what we would expect from what the tooltip says, "4% Damage Resistance per stack". If the buff would have been additive we would have this


Effectiveness = 100% * (1 - (0.5 + sum(temp_buffs))
Effectiveness = 100% * (1 - (0.5 + 0.04))
Effectiveness = 100% * (1 - 0.54)
Effectiveness = 100% * 0.46
Effectiveness = 46%


The 3rd attack has 2 stacks of shadowclad buff, 50% DR from defense, no deflect, no debuffs
Effectiveness = 100% * (1 - 0.5) * (1 - 0.04) * (1 - 0.04) = 46.08%

That's a 4.08% difference of what we would expect, as you already start to see, each additional stack becomes less and less effective and deviates further from what the tooltip says. If an additive method was used instead we would get


Effectiveness = 100% * (1 - (0.5 + sum(temp_buffs))
Effectiveness = 100% * (1 - (0.5 + 0.08))
Effectiveness = 100% * (1 - 0.58)
Effectiveness = 100% * 0.42
Effectiveness = 42%

With 2 stacks of 4% DR buff (8% total) we would expect to see a value of 42% here instead of 46.1% in act due to rounding up from 46.08%


Here's some screens of when I used Negation, the logic is similar except each negation stack is 1.2% and it stacks differently w/ icd's and such.




I'll leave the maths to the reader on this one.


Here's the log file on dropbox
https://dropbox.com/s/nplutojo55i6c7o/Combatlog_2019-06-05_20-00-00-Xeros-Negation_Shadowclad.Log?dl=0

The first encounter is w/ shadowclad, the second is with negation.