Rogues and Armor Penetration

I just wanted to say hi to all the guilds, like Icon, Shadow Fate, Team Deathwish and Aequitas, linking to this post. Please feel free to post a comment and look around at the rest of the site.

There have always been abilities that have reduced your target's armor, and, there has been gear that has allowed you to ignore your opponent's armor, primarily from high level instances like Black Temple, but it is my opinion that with Patch 2.3, Armor Penetration will be considered by more and more players.

Rogues aren't the only class that is going to get Armor Penetration. All melee classes are getting it. However, Rogues also have the Expose Armor ability and Serrated Blades talent in our Subtlety tree. As many Rogues are going Subtlety, I thought I'd give a quick rundown on how Armor Penetration works and what sort of improvement you're going to see from it.

First, you need to realize that some of our attacks don't even consider armor. So, for the rest of this post when I talk about DPS, I'm speaking of DPS that is affected by your target's armor.

Here's a list of the damaging abilities we possess that don't consider armor:

• Garotte
• Rupture
• Poisons
• Envenom

Next, how does Armor work? At level 70, World of Warcraft uses the following formula to determine a character or NPC's damage reduction (or mitigation) from armor.

Damage reduction =	Armor
	(Armor + 10557.5)

Thus, the more armor you have, the less damage you take from attacks. Makes sense, right? Stacking on more armor has a diminishing return effect for the increase to your mitigation. However, your increase to your time to live remains constant as you add armor. For each 1000 armor, you increase your TTL (time to live) by 9.47%. Damage mitigation from armor is capped at 75%, so having more than 31672.5 armor doesn't gain you anything.

How does Armor Penetration work? It simply removes armor from your opponent and recalculates their mitigation before your attack. If your opponent has 7700 armor and you have 1500 Armor Penetration, they only have 6200 armor versus your attack. They go from 42.2% mitigation to 37%. Therefore, you've increae your damage against them by 5%.

With Patch 2.3, Rogues are receiving 11 new pieces of gear that will feature Armor Penetration.

Slot	Name	Source	Armor Penetration
Back	Dory's Embrace	Badges of Justice	112
Waist	Bladeangel's Money Belt	Zul'Aman	77
Ranged	Ancient Sin'dorei Longbow	Zul'Aman	126
Finger	Signet of Primal Wrath	Zul'Aman	126
Chest	Shadowtooth Trollskin Cuirass	Zul'Aman	210
MH Weapon	Prowler's Strikeblade	Zul'Aman	140
MH Weapon	Dagger of Bad Mojo	Zul'Aman	140
MH Weapon	Vengeful MH	Arena	49
OH Weapon	Vengeful OH	Arena	49
Head	Vengeful Gladiator's Leather Helm	Arena	84
Legs	Vengeful Gladiator's Leather Legguards	Arena	84
Finger	Vindicator's Band of Triumph	Arena	56
Chest	Vengeful Gladiator's Leather Tunic	Arena	84
	Total Max from Gear		1155

That's a lot of gear being introduced that has Armor Penetration. You can get about 1200 Armor Penetration. But you are probably wondering, "How does that correspond to DPS?" Well, after a bunch of math, I came up with the following graph:

Click for an expanded chart.

The way to determine you DPS increase from Armor Penetration is first find your Armor Penetration total on the bottom (x) axis. Then, find the line corresponding to your target's current armor total.

Example

So, say you have 1715 Armor Penetration (1155 from the gear above and another 560 from Serrated Blades) and your opponent is a boss in Serpentshrine Cavern that you know currently only has 3690 Armor because Warriors applied 5 Sunder Armors (-2600 Armor), Druids cast Faerie Fire (-560 Armor) and Warlocks applied Curse of Recklessness (-800 Armor).

Find 1715 on the bottom axis and then finding the 3000 and 4000 armor lines. 3000 is near 11% and 4000 is near 9.5%. So, I'd guess about a 10% boost to DPS. The actual value is 10.14%.

A couple of quick facts arise from analysis at this data:

• The more Armor Penetration the better. It's not a diminishing return, but rather an increasing return.
• The less armor your target has the greater benefit you get from Armor Penetration and every additional point of Armor Penetration.
• Every ability that your team uses to reduce your target's armor helps your Armor Penetration.

Outside of gear and Serrated Blades, we also have Expose Armor and the corresponding talent Improved Expose Armor. Expose Armor negates 410 armor per combo (512.5/615 with each points of Improved Expose Armor respectively). This doesn't stack with a Warrior's Sunder Armor and is the reason why it isn't widely used. However, if you examine the graph for a 2050 Armor Penetration (normal 5 combo point Expose Armor), you can see that you're getting 7-16% increase in your DPS once applied and, with a Rank 2 Improved Expose Armor, you're applied a 3075 armor debuff for a 11-22% increase in DPS.

Also new in Patch 2.3, the Executioner Enchant can be applied to any weapon and will occasionally proc the Executioner self-buff which will add 840 Armor Penetration for 15 seconds. These do not seem to stack and they have been reported to proc about the same rate as Mongoose, or about 1 proc per minute. Most reports I've seen seem to report that Executioner will result in lower DPS than Mongoose, but these tests seem to be judging Executioner vs Mongoose in a vacuum of many of the other factors that are going to come into play during both Arena and PvE.

Here's a few more items that I found that have Armor Penetration:

Icon of Unyielding Courage Binds when picked up Unique-Equipped Trinket Requires Level 70 Equip: Improves hit rating by 30. Use: Your attacks ignore 600 of your enemies' armor for 20 sec.

Warp-Spring Coil Binds when picked up Unique Trinket Classes: Rogue Requires Level 70 Equip: Improves hit rating by 21. Equip: Your special attacks have a chance to give you 1000 armor penetration for 15 sec.

As I go into Patch 2.3, I plan to evaluate this firsthand and I'll report back with what I find. I would love to hear other Rogues' encounters with Armor Penetration as well.