AeroWow

So, Armor Penetration.  What’s all the rage about?  (My first Warrior pun!)  There seems to be plenty of the stat floating around on our gear nowadays, so is it really worth investing in, both now and in the foreseeable future?

I’ll admit, the first time that I saw Armor Ignore back in the Burning Crusade, I was a little less than impressed.  ”I can ignore 50 armor off of a boss with thousands of armor?  Awesome.”  Once I took a look at the math behind it, though, I realized just how good it was.

See, armor is great as a defensive stat – it reduces the incoming physical damage on a character or mob by a certain percentage, depending on the amount of armor present.  Logically extending the armor mechanic, if you can reduce the amount of armor on a target, as the attacker, you can increase your damage output by removing their defenses!

Ignore Armor did exactly what its name suggests: your attacks would ignore a certain amount of armor on your target.  With 50 Ignore Armor, your attacks would simply subtract the target’s armor by 50.  Sunders and Faerie Fire took off a static amount, as well.  When everything started adding up, it got to the point that the more Ignore Armor you had, the more valuable it was!  Once Ignore Armor levels were up to roughly 600 (your attacks would act as if your target had 600 armor less than it would otherwise), it was the absolute best stat to stack.

With the advent of Wrath (actually, patch 3.0.2), Ignore Armor turned into Armor Penetration (ArP) – and the mechanics drastically changed.  Instead of taking off a flat amount of armor, ArP now is a rating, which takes off a percent of the final armor your target has.  This is a total shift from the days of Ignore Armor, which would take off the same amount of armor, if it’s a cloth wearer with a few thousand armor, or a plate wearer with over ten thousand (BC values, same concept applies).  This completely changes the value of ArP, and how it works when computing how much damage you do on a given target.

So, let’s take a look at how ArP works, both currently, and in the upcoming 3.1 patch.

Currently (live, 3.0.9 patch, Sunders and Faerie Fire still take off a flat amount of armor), a level 83 raid boss has 13083 armor.  Fully debuffed, the boss now has [13083 – (5 x 785) – 1260] = 7898 armor.

Now, we have a new base boss armor that our ratings work off of – 7893, as opposed to 13083.  This is very important to determining the effect of our ArP! Because ArP is rating, it affects the armor by taking a percent off the target’s final armor for computing purposes.

So, a boss has 13083 armor, no debuffs. Let’s say I have 20% ArP.  [13083 x (1 - .20)] = 10467.  That’s a reduction of 13083 – 10467 = 2616. So, my ArP of 20% translates into a 2616 armor reduction.

Let’s compare that ArP result with a fully debuffed raidboss.  Looking above, the boss has 7898 armor, after Sunders and FF.  [7898 x (1-.20)] = 6319. The same 20% of ArP now reduces the boss armor by 1580. This value, the one shown in this paragraph alone, is the real value of ArP on 3.0.9 servers.

So, final analysis?  ArP on the live realms is good.  Not fantastic, but not terrible by any means!  Also, as opposed to Burning Crusade’s Ignore Armor mechanic, Armor Penetration affects all targets equally, relative to their total armor.  If you have 20% ArP, a Mage get 20% off of their base armor, and a Prot Warrior gets 20% off of his armor.  Of course, these two targets are impacted differently, as 20% of a small amount of armor is certainly different from 20% of a large amount of armor, but the PvP aspect of ArP is a separate discussion entirely.  The key here is that ArP is now a rating, and is a good statistic on physical DPS gear (for those classes/specs that rely on primarily physical damage).

Now, how will this change come 3.1? Armor Penetration is being drastically revamped, for the better. Firstly, Sunder Armor and Improved Faerie Fire are no longer flat amounts; they are percentages (20% and 5%, respectively).  Secondly, to keep the balancing of Armor similar, the base boss armor has been reduced (to 10645), which keeps everything more or less equal, when comparing the boss armor after Sun/FF.  Thirdly, ArP now gets 25% more value from the rating – you will get more ArP bang for your itemization buck.

So, we have a new formula to plug our values into:

Base Armor x [(1-.20) x (1-.05) x (1-ArP)] = Final Armor
Base Armor x [Sunder x FF x ArP] = Final Armor

Formerly, we were working with a boss that had 13083 base armor just standing around, and 7898 debuffed.  Now, we have a boss with 10645 base armor, and [10645 x [(.80) x (.95)]] = 8090 debuffed.  A slight increase in armor.  But let’s see how our ArP works now:  [8090 x (1 - .25)] = 6068.  Compared to the Live result of 6319, this is a significant buff to Armor Penetration.  As ArP continues to get more and more valuable as your start reducing the target’s armor closer and closer to zero, it is a very stack-friendly stat.

What does this mean in tactile, usable terms? It means that, whatever value you currently give to ArP on the live servers, increase that value by about 30%.  If your current EP of ArP is at .6, it’ll be worth around .8.  This puts ArP as valued almost alongside (not quite, but close!) your primary stats of Strength and Crit, and solidly above its secondary stat “counterpart”, Haste.

“Okay,” my imaginary reader asks.  “So, after wading through that mess of information, what does this mean for me, as a rank-and-file raider that actually spends DKP on the stuff you’re talking about?”

It means you have a new stat to try and balance.  You now have another cap to work towards (not hold yourself to, yet), the ArP soft cap.  With the Grim Toll as a trinket, there is a soft cap: the amount of ArP you need so that the massive amount of ArP granted on the Grim Toll’s proc does not put you over the ArP cap (armor cannot be reduced below 0, after all!).

It means you should start picking up any gear you come across that has Armor Pen on it, if you haven’t been already.  Grim Toll, Legplates of Double Strikes, just start accumulating Armor Pen gear that happens to drop.  It’s that simple – if it has ArP on it, pick it up on the cheap.  This doesn’t mean you’ll 100% be sure that it’ll be in your Ulduar gear set, but at this point in the game, most of you will simply be saving gear from shardification (I am the Shardifier for about 50% of my guild’s raids, and always hate to see over half a night’s loot turned into glowing purple crystals).  Save the gear – invest in your future – start picking up ArP pieces for tomorrow!

UPDATE! Much of the particular numbers contained within this post are now out of date. I plan to take another, fresh look at ArP soon, which will include all of the new numbers, caps, and all that fun stuff. While the numbers in this post may not be accurate, the general concepts still mostly apply.

References:

Corb’s 6th Edition Dual-Wield Fury Guide (With extensive ArP work by Jathine)

Kalroth’s Simple ArP Calculator

PS . Keep in mind that there are currently numerous bugs with Armor Pen on the 3.1 PTR at the moment.  I’m going to stay up with the latest developments, and will be sure to note if anything major happens that drastically affets the gearing impliations on the material covered here.

PPS.  Note that any talents and stance benefits are multiplicative.  You cannot add them into the ArP factor, they are instead calculated like so:

Base Armor x [(1-.20) x (1-.05) x (1-.08) x (1-.15) x (1-ArP)] = Final Armor
Base Armor x [Sunder x FF x Battle Stance x Mace Spec x ArP] = Final Armor

This is where you may see additive versus multiplicative coming into play. All this means is that the bonuses are multiplied (e.g., Sunder x FF), or additive (e.g., ArP from all gear is added together to come to the net gear ArP value).  While these additional sources of armor reduction do indeed “water down” the benefit of one’s ArP from gear by lowering the amount of armor your ArP affects, they should not be put aside outright.  That’s the equivalent of saying that Sunders or Faerie Fire should not be present on a target, because they reduce the contribution of your ArP from gear.  These buffs still help increase your damage output.  For more accurate and simple calculations of numerous buffs, a spreadsheet or calculator (like the one above) comes in mighty handy.