I think GC’s post has all we need to undestand ArP, and it’s quite clear too:
“Another way of understanding that is we multiply the percentage in the tooltip times the minimum of the two values: the cap, and the amount of armor on the target after all other modifiers.”

So we have to take the minimum between the lvl 83 boss cap (which is, as stated above, 8625, using the correct C=15232.5), and the boss armor after the modifier (sunder), which is: 8514.

As you can see, 'boss armor after sunder' < cap.
This mean we can actually bring the boss armor to 0.

Again this means that the only cap for ArP rating is:
ArP from gear + talents/bonuses + Grim Troll proc < 100%


“So, we decided on a system where there is a cap on how much armor the Armor Penetration Rating can be applied to. So, the first X armor on the target is reduced by the percentage listed in the Armor Penetration Rating tooltip, and all armor past that X is unaffected.”

It is therefore useless to stack ArP rating over 100%, as Blizzard by design intended that a part of boss armor isn' affect by ArP rating. It's furthermore useless since in most cases you'll have sunder applied to the boss, and a value >100% would take the armor below 0, which is absurd.

TL;DR - Your 100% boss armor removed figure. PvE Cap = 1158 / 546 (battle).
Fury can never cap in a raid setting, topping off at 1232 ArP (620 w/ GT) giving 98% armor removed.
Thanks and I'm glad to help out. For some reason I got obsessed over ArP and couldnt' stop running tests and calculations until GC posted, lol.

----

I still like our ArP formula that Rallik derrived until someone can show it no longer models sunder+ArP effectively.
It's got the closest match to all my dummy data. The only real addition that GC provided was explaining the 19% suppression and where it came from, and giving us the exact numbers on the 80 dummy and pvp (though we were close on the 80 dummy). Granted, figuring it out with all the specifics would have taken a while.

Landsoul's rewrite of Rallik's formula, modified with GC's info:
(bear with me if it doesn't display properly - I browse forums with graphics disabled at work)

/frac{A}{(A+B*((1-Zx)-y*(1-(/frac{B}{(A+B)})*Zx)))}

A = 15232.5
B = 10634
x = ArP rating / 12.316 (tooltip ArP) capped off at 100%, then with 10% (battle) or 25% (battle+mace) added to it
Z = /frac {A+B}{3B} (that's the percentage of removable armor, AKA the "suppression factor")
y = 1 - (armor remain after debuff1 * armor remain after debuff2 * armor remain after debuff3) etc. E.g. 1-(.8 * .95) = .24 for 5Sund+FF

Anyhow, put in all the raiding values, y=.24 and the 10% battle and solve for x and you get 1158 ArP cap. (546 w/o GT)

That's yourr 100% boss armor removed figure. PvE Cap = 1158 / 546 (battle).
Fury can never cap in a raid setting, topping off at 1232 ArP (620 w/ GT) giving 98% armor removed.

Hopefully that helps.

Me (or anyone else) still needs to test numbers vs various pvp armor values +sunder to verify the formula at high ArP values and against high armor numbers, and doublecheck that the tooltip cap is 100%.

[edit: Thymolean, do you mean that battle stance does not allow x to go to 1.10? I'm somewhat confused about exactly what you're saying. Do you just mean that GC's implication was that only Tooltip ArP capped at 100% and that battle/mace could go above it, but not so far as to remove all armor?]

I don't believe there is a cap to Armor Penetration.
I did some simple tests today with Slafsinator and we got mobs to negative armor.

Data
Attack power: 2745
Gear + food + elixir: 50.91% (627 rating)
Character sheet ArPen with Grim Toll proc: 100.60% (1239 rating)
Battlestance: Yes (makes it a total of 110.60%)
Sunder Armor: 5x
Thunder Clap, base value: 629.4
Heroic Throw, base value: 1385

No damage modifying talents such as Blood Frenzy, Wrecking Crew or 2H weapon spec was in effect.
You can see what items and talent spec I used on my armory profile (only for today though, I'm not going to be allowed in raids with my current spec! :)

We used this spreadsheet for numbers.

Results
Against a level 80 mob with 9729 armor (Hulking Abomination in Icecrown, just outside Dalaran)

Damage values with Grim Toll proc and 5x Sunder Armor
Thunderclap hits for: 660 damage
Heroic Throw hits for: 1452 damage

This matches our data of -702 armor on the target.

Is that negative armor increases damage taken? That is very interesting. If there really is a cap past a certain point ArP would just be insane wouldn't it? I wonder if it goes the same way as negative resists.

Kalroth, your armory link shows you having 2H weapon spec. You sure you did your testing without it?

100% - I did all tests with my current weapon, Last Laugh.

Granted, it's possible that bosses armor functions differently than regular mobs armor. However, that is less likely, and if you can do additional damage against negative armor targets then it would apply to bosses, it would just be harder to get to that value.

Kalroth, have you done any additional testing? If you were inclined to do some, could you provide combat logs and screenshots of your tooltips?

Yes, I did more testing tonight as I got more ArPen gear to test with, you can see the results here:
http://elitistjerks.com/f31/t29453-c...8/#post1210542

And I also took a screenshot while hitting the level 80 mob: http://eu-warrior.com/WoWScrnShot_042409_000548.jpg
You can see the Heroic Throw damage to the right and remember that the battle stance bonus is not included in the tooltip.

I don't remember anyone saying that boss armor and mob armor are different. It should be testable with a dummy though.

A level 80 mob doesn't have the same armor as a level 83 boss.

I meant that the mechanics are the same, the values are different of course.

The spreadsheets here are probably much more accurate than maxdps will ever be. Maxdps should be a general guide at most, and not used at all for individual item comparison.

My data completely supports Kalroth's statement for ArP values that exceed 100%. He nailed it, and nice find.
ArP is not ever capped at 100%. You keep removing armor. Even if you have no stance or spec bonus to ArP.

I used a 10-31-0 testing spec with BT. I ran the tests once without elixir/food and once with the +85 ArP from those buffs.
I had 1391 BT base on the gear I ran, no procs other than Grim Toll which could confuse math.

Level 80 dummy tests (e.g. 9729 armor)

Test Case	1316 ArP	1401 ArP
_________	________	________
Zerk+0S	1318	1367
Battl+0S	1390	1444
Zerk+5S	1429	1482
Battl+5S	1508	1567

Level 83 dummy tests (e.g. 10643 armor)

Test Case	1316 ArP	1401 ArP
_________	_______	________
Zerk+0S	1271	1319
Battl+0S	1341	1394
Zerk+5S	1385	1437
Battl+5S	1461	1509

Just to make sure that without sunder/battle I could still bring a target to negative armor, I hit a guildie rogue with 5801 armor for 1427 in zerk with 0 sunders at 1316 ArP, same 1391 Bt base.

All of my test data matches Kalroth's spreadsheet.
Data indicates these conclusions:
* There's no cap at 100% tooltip ArP (or else using elixir/food would have done nothing).
* With enough ArP, you can bring a target to negative armor. Even off of just pure ArP rating and no talents/stance.
* It is possible to bring targets to increasingly negative amounts of armor if you can get enough ArP.

Armor #	Bonus Dmg
-1000	+7%
-2000	+15%
-3000	+25%
-4000	+36%
-5000	+49%
-6000	+65%
-7000	+85%

you get the idea.

This is fairly likely to get nerfed, so be careful just how much time and money you spend on it.

I logged out in my testing gear and spec (cept I used a broken promise with a weapon chain instead of BoH, cuz procs are annoying for testing with a small window like GT), in case anyone wanted to check up on me to make sure I didn't throw in a mistake. I was the only one hitting the dummies. ( The World of Warcraft Armory )

I take these numbers would result in Executioner being a really good enchant again given that you're walking around in proper arp gear?

I guess eventually... does anyone have the proc rate on executioner? You'd need a really huge amount of ArP or for executioner to have a vhigh proc rate for 10% ArP to be better than 400 AP at 40-60% proc rate...

A player with ~50% ArPen from gear plus food and elixir in battle stance will gain ~6% dps when Executioner procs. If you're lucky enough to have Grim Toll proc at the same time, then Executioner is a 9.5% dps gain.

I've updated my armor penetration calculator according to latest changes and findings: Simple ArPen calculator

EDIT: Additionally I would also like to blame Slafsinator for the findings. He created the Excel sheet, I am only an arpen lootwhore with enough gear to prove his ideas. :)

In general the post is very useful, except it spawns/can spawn a couple of unfortunate assumptions:

• Armor Penetration is capped at less than the mob's base armor (it's not, it doesn't seem to be capped at all)
• Armor can't go below 0 (it certainly can)
• Armor Penetration is capped at 100% (it's not)

Useful info from the post:
• Armor Penetration doesn't get its full benefit against high armor targets (yet it's still effective)
• Armor Penetration is predictable and does work even though it sometimes differs from what you might've expected.

Slafsinator, there are a few things i do not understand about the ArP calculator.

Firstly, at 42% ArP from gear with sunder, FF, battle, hearty rhino, elixer of armor piercing, grim toll and executioner all checked off i get a result of -1173 armor 84.04% damage increase. Now if i add in shattering throw, the total of armor reduced actually decreases to -1072 with a 82.73% damage increase. I cannot comprehend why the calculator does this. If there is no cap shouldn't the damage increase keep going up?

Also how do i go about figuring out when/if mace spec will outweigh poleaxe or if executioner will outweigh berserking?

I posted on this exact issue in the Combat Ratings thread.

Summary: The closer the armor of the target after debuffs is to the so-called Armor Penetration cap, the better off you are once you cross over into negative armor land. Shattering Throw reduces the target's debuffed armor and thus the excessive Armor Penetration stacking yields less negative armor gain.

Hey err'one,

will fury be better than arms with some better gear? atm i am arms, but at bosses like hodir were u have a lot movement, it really suxx to hold my rota up.

I really loved playin' fury, but arms is nice too.

Well, i just want some advices. :P


Tora


ps.: sry for my bad english.. :P

Also, if I read the code behind the calculator right do Sunder Armor and Faerie Fire stack additively then?

There seems to be an error with that in the calculator. All debuffs stack multiplicatively.