Armor Penetratation - Lack of a Cap?

There are caps to armor pen, but the total amount of armor that can be reduced is not one of them. The numbers you need to really to get armor pen to the point where it feels broken cannot really be done with available gear.

Q u o t e:
How is there a cap to Armor Pen but not the effect? I'm confused.

There is a cap per point. You can't ignore more than a certain percentage of the armor per point. This is what keeps armor pen from being better vs. targets with lower armor.

There is no cap on the amount of armor pen from which you can benefit. More points of armor pen always give you more damage (in the way more AP always gives you more damage, but more hit does not).

We are familiar with some of the theorycrafting for how great armor pen might be for fully Ulduar-geared melee. We're not worried about it yet because it's a big improvement over armor pen being a junk stat, which is where it was for many until recently.

We're not too worried about the double trinket proc in PvP. It's impossible to use on demand, you have to give your PvP trinket to do it, and it still isn't better vs. lightly armored targets, which is what we wanted to fix.

We are now considering capping armor penetration at 100%. Armor could no longer go negative. We're not sure if we would do this in a hotfix or in 3.1.2. We just wanted to let anyone know who is furiously trying to acquire every armor pen item in the game.

Note that there is not a not a cap on the amount of armor that can be reduced in WoW at the moment. Also note that capping armor penetration at 100% does not mean that you can always reduce every target's armor to 0%. The tooltip says "up to" for a reason.

Yes, we understand this stat can be a little confusing.

Q u o t e:
What happened to:
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Q u o t e:
There are caps to armor pen, but the total amount of armor that can be reduced is not one of them. The numbers you need to really to get armor pen to the point where it feels broken cannot really be done with available gear.

We started to take a look at the next couple of tiers of gear.

Q u o t e:
But if I'm understanding this right, you will still see a gain from Armor Penetration rating up to 1231 Armor Penetration Rating (100%) even if the target is under the effects of Sunder Armor (assuming no other abilities effecting Armor Penetration)?

Yes. Even against a fully sundered target, armor pen will still improve your dps. For nearly all reasonable cases, it remains a good stat unless you are a class or spec that does a high amount of non-physical damage. The cases were you could currently go negative are very contrived and involved stacking armor pen at the expense of all other stats and hoping your procs all go off at once. We can’t imagine this will be a nerf for anyone currently in the game.

Q u o t e:
This is troubling - if only because even with the stat as currently constituted, warriors do not appear (and by that I admit that 'appear' is from parses and possibly rampant hyperbole) to be as of yet really competing on the charts.

Stacking armor pen at the expense of all other stats is not a reasonable or intended way for warriors to “catch up” to rogues. It’s still a good stat for warriors.

Q u o t e:
Most of the classes who can use this stat don't want it. Finally, it becomes semi-useful to very few classes and then you nerf it so it's useless again?

We made armor pen a better stat in a previous patch. I am fairly confident that many of the posts above decrying this as a nerf are over-estimating how close to removing more than 100% armor you really were. Even if you have two armor pen trinkets and they both proc simultaneously, that is going to be very low uptime. This is not a nerf. It's a preventative measure to keep things from breaking at future tiers of gear or in really exotic situations.