Arena Season 3 is coming soon, and recent posts by developers have hinted that we will be seeing armor penetration included on PvP gear for the first time. This is a welcome addition to the item budget in the offensively weak PvP sets of physical DPS classes, but just how far does each point of armor penetration go?

What we'll expect of the gear

This forum post from Kalgan informs us that, "All the armor penetration on Season 3 melee gear adds up to less than 910." You can consider an estimate for 1000 armor penetration to be very close for a fully-geared Season 3 character. The Serrated Blades talent in Subtlety adds 560 passive armor penetration, a new "Executioner" weapon enchant will proc for 840 armor penetration, and there are a few other items (mostly trinket) that can proc for some armor penetration as well.

How armor penetration will scale

While the idea of armor penetration seems like it would be geared toward bringing down heavily armored targets, the ingame effect is unfortunately reversed. Armor penetration, much like expose armor, will be stronger on low-armor targets, weaker on high-armor targets.

Who does this help the most?

If we consider all classes in the big picture, armor penetration is obviously a buff to all physical DPS classes. Relative to each other, however, the physical DPS classes fall into a very clear hierarchy. As mentioned previously, the stat is more powerful against low-armor targets, so in any given physical-physical matchup, the player with higher armor is getting a bigger benefit from armor penetration.

For example, Warrior versus Rogue. Let's assume both players have 2000 armor penetration. Due to armor penetration, Warrior does ~16% extra damage to the Rogue, while the Rogue does ~11% extra damage to the warrior.

In the end, we can confidently conclude that Warriors get the most benefit from armor penetration as their damage will always be buffed from armor penetration by the same amount or more than their enemy target's damage. Feral-spec Druids in bear really benefit most, but they are not in bear form full-time, so Warrior will get more mileage out of the stat.

Due to the natural armor hierarchy, we have the following:

Order of buff strength from Armor Penetration

1. Feral Druid (Bear)
2. Warrior
3. Hunter / Enhance Shaman
4. Rogue / Druid

Breakdown by numbers!

As a reference, I have prepared a table of data so you can look up just how much physical DPS you will gain from a given level of armor penetration on different targets.

First, a calculation of DPS increase for a range of armor penetration values:

Rough DPS Increase from Armor Penetration*

Target Class	1000 pen	2000 pen	3000 pen	4000 pen
Cloth, Rogue, Druid	7.38%	15.93%	25.96%	37.89%
Hunter, Enh.Sham	6.04%	12.86%	20.61%	29.50%
Plate+2H, Sham+Shield	4.86%	10.23%	16.17%	22.78%
Plate+Shield	3.91%	8.14%	12.73%	17.73%
Bear Druid	3.38%	7.00%	10.89%	15.06%

*According to Kalgan on WoW forums, the ful set of Season 3 gear will have something less than 910 Armor Penetration.

I have created a full spreadsheet that will allow you to look up these values by target armor value and amount of armor penetration, and I have it hosted for public view at Google Spreadsheets.

View the full spreadsheet here