Hey hey,

so negative resistance works, if you got a sunder.
The order of computation of the resistances is as follows:

1. Sundering the Immunity
--> The value of the immunity goes to 95, whatever the immunity value has been before.
2. Enemy XXX resistance lowered by X% from Gear/Items
--> This lowers the resistance 1:1 the amount of percent it is displayed
3. Enemy XXX resistance lowered X% from Skills (no matter if passive like Cold Mastery or active like Conviction, Lower Resist etc.)
--> This lowers the resistance by 1/5 of the value.

Example:

Cold Sorc with Cold Rupture (cold sunder charm), -15% Enemy cold resistance from gear (for example Nightwings Veil) and Cold Mastery at Skill Level 17* which brings -100 enemy cold resistance
Enemy cold resistance for this example: 215%

1. Cold immune enemy gets his immunity sundered by the charm
Cold resistance value: 95%
2. Enemy cold resistance lowered by 15% from gear
Inital cold resistance after sundering minus negative cold res from gear = 95%-15%=80% | Remember: negative XXX Res from gear gets taken away 1:1 from enemy res
Cold resistance value: 80%
3. Enemy cold resistance lowered by 100% (Cold Mastery)
Cold resistance after second computation minus 1/5 of the resistance lowering effect of cold mastery = 80%-(100/5)=60% | Hint: This works for all passive/active skills in the same way, always a fifth of the displayed value
Cold resistance value: 60%

I hope you are able to fully understand what I wrote.

Feel free to ask me any questions :)

thanks for your nice words acting like everyone here is stupid

thanks for all the replies, much appreciated.
ill have a go on maxroll see what's better. Not sure where i should be finding the legit answers though xD

Little add on:
Depending on your gear, you need to (if you wish to :D) calculate the amount of resistance an enemy has without the +/- percentage of your renewed sunder charm to find an answer to your question.
If you have a rest immunity of 70 cold res with cold immune monsters after sundering and the computations we did before, 1% of negative enemy resistance from the sunder charm will result in +0,7% enhanced damage (based on the 70 cold res: 1% of 70=0,7%) for your cold skill damage, whereas this value will be higher with non cold immune monsters, which have a regular inital immunity of less than 95%.

Little computation for that:

100 cold damage dealt to a 70% cold immune monster = 100-70%=30 cold damage dealt
With -1% enemy cold resistance: 100-69,3=30,7 damage dealt

Whereas if you decide to take the +1% cold damage:
101 cold damage dealt to a 70% cold immune monster =101-70%=30,3 cold damage dealt

You need to assess your rest resistance of "cold immune" enemies in order to make a decision.
Depending on the numbers it could be better to take -X% enemy cold resistance over +X% Cold Skill Damage.

Without me boring you guys with numbers: If your remaining enemy cold res is above 50 points, take -X% Enemy Cold Resist. If below 50, take +X% Cold Skill damage.

this looked like a nice calc until you said "-15% Enemy cold resistance from gear (for example Nightwings Veil)"

-10% cold resistance all the way. Cold immunes are always the bottleneck. You can forego doom and use death fathom for everything. DF offers more than enough cold damage.

Hahaha got me!
I have had a long day. I somehow mixed up + and - xD

But rather than that its very obvious how its calculated.

minus

Thanks for all the feedback, after some math it worked out minus is going to be better for quite some time, sold the +dmg to gear up elsewhere. 👌

It depends on your current build and what you are doing (as well as your pcount).

If you are target farming a boss/area, you'll want your total cold pierce to be whatever their CR is + 100 (for mephisto, you'd want 175 total). Once you have that # total cold pen, go for +cold dmg.
If you are TZ farming, keep reading.


There are about 440 "base" monsters (different names & resistances, e.g blood clan in tower cellar & blood clan in halls of pain).
About 130 are innately cold-immune (29.5%, but with affixes the actual percentage is higher).
7 have between 80 and 95% cold resist (duriel).
25 have 70 to 75% resist (mephisto).
8 have 60 to 66% resist (andy).
66 have 40 to 50% (baal, diablo).
40 have 33%.
39 have 15 to 25%.
120 have 0% cold resist.


Of the non-cold immunes,
~38.7 are at 0.
~51.3% are 25 or less.
~64.2% are 33 or less.
~85.5% are 50% or less.
~88.7% are 66% or less.
~96.8% are 75% or less.

With these numbers, you get to decide where you want your damage.
Do you want more dmg on every monster (+cold dmg) or more dmg on some monsters (-enemy resist)?
For a standard build. the optimal total cold pen spot, where 1% cold pen = 1% cold dmg for dps across all monsters is 150. Once you hit 150, more cold pen will have less return on your dps over more cold dmg (cold pen will have MORE impact than cold dmg below 150 cold pen).

Another thing to consider is what is slowing you down the most. If non-immunes are already getting 1-shot, any extra damage won't make a difference on them. And if they are getting 2-3 shot, then 15% won't make a noticeable time difference either...



tldr;
Aim for 150 cold pen before boosting dmg (via synergies or items).
If you are using high end doom & proctor frost & nw & facets, I would suggest +15% dmg. If you have fathom (or something else), -10% resist will almost certainly be better.