"Dude, I've got two almost identical pieces of chest-armor, one has more Crit and one has more Armor Penetration. Which of these should I equip: the Gilded Ringmail Hauberk or the Razorstrike Breastplate?"
"Dude, you need the Armor Pen! Grab the Hauberk, the Armor Pen-chest!"
"Seriously, you think Arm Pen is good?'
"Dude! It's so sweet! It reduces the enemy's armor so it totally ramps-up your DPS!"
"Sweet! I'm totally down with the Hauberk."
This is what it sounds like, when Hunters cry.
An enemy's armor protects him from physical damage. If we can reduce that armor, our physical attacks will inflict more damage. Any problems with that? Sounds pretty simple, yes?
Blizz permits us two mathematical ways to reduce an enemy's armor: we can reduce a flat amount or a percentage.
Warriors use Sunder Armor to reduce a flat amount of armor. If a warrior is able to stack five Sunder Armors, he will reduce the enemy's armor by 3925; a flat amount. If the enemy has 4000 armor before the attack, he'll only have 75 armor to reduce incoming physical damage. Nice.
Hunter use Armor Penetration to reduce a percentage of armor. At level 80, a hunter requires an Armor Penetration rating of 15.38 to reduce an enemy's armor by 1%. If a hunter has an Armor Penetration rating of 154, and he attacks a different enemy that also has 4000 armor, the hunter will reduce the armor by 10% -- 400 -- and leave the enemy 3600 armor to reduce incoming physical damage.
Warrior have it easy; nerf warriors, right? Don't worry, we're going to dislike them even more later.
But let's pretend our enemy has a lot more armor, like 13,000. Now a warrior still reduces that by 3925, leaving 9075. Our hunter faces a different mob whose health armor is also 13,000, so the hunter reduces it by 10% -- 1300 -- leaving 11700.
Notice that previously we said the warrior and hunter were attacking two separate enemies. Well that's not how we raid, is it? The warrior and the hunter are usually attacking the same mob. And this is where a hunter's armor penetration takes it in the keister.
Armor Penetration is calculated using the mob's acting-armor, not his base-armor. Sunder Armor is calculated upon the mob's base-armor, not his acting-armor. What this basically means is that Sunder Armor is calculated first.
We grab our mob with 13,000 armor. We know that the warrior's Sunder Armor reduces it by 3925, leaving 9075.
When the hunter attacked his own 13,000-armor mob, the 10% armor penetration reduced the armor by 1300. But when the hunter attacks the mob that the warrior is attacking, the armor penetration is calculated on the post-Sunder Armor value of 9075. Our Armor Penetration is going to reduce that value by 10% -- 907 -- leaving the mob with 8168 armor.
Well that's not bad, but it's certainly not what we wanted. We wanted 3925 from the warrior and 1300 from the hunter. But since Armor Penetration is calculated on the mob's acting-armor, we only reduced the armor by 907, not 1300. Our Armor Penetration rating, which we worked so hard to raise, has had its value reduced from 10% to just 6.98%, (907 / 13000 = 0.06979 or 6.98%).
6.98% instead of 10%? That's more than a 30% decrease in value from our armor penetration gear! And that, frankly, stinks. Even worse, there is another component to this debacle, and that has to do with the squishiness of the enemy. Observe, again.
For a mob with 13,000 armor, our 10% Armor Penetration was reduced to 6.98%. But what if we're fighting a mob with just 6000 armor?
The warrior still reduces that by 3925, leaving 2075. Now the hunter's Armor Penetration is applied, where 10% of 2075 is 207, reducing the enemy's armor to 1868. But reducing 6000 armor by only 207 is a reduction of only 3.45%!! (207 / 6000 = 0.0345 or 3.45%) Geebuz, that's a positively massive decrease from the 10% armor reduction we see on our tooltip.
The bigger the warrior's Sunder Armor, the less effective our Armor Penetration is. The squishier the enemy -- i.e. the less armor he has -- the less armor-reduction-efficiency our Armor Penetration returns. Basically, the more Armor Penetration rating we hunters stack, the less value we get for our efforts. Stinkin' warriors...
So now we return to our choice of armor: the Armor Pen chest or the Crit chest.
Crit is Crit, right? There's nothing anybody in our raid can do can decrease how effective our Crit is. When a hunter crits, he does more damage and generates Focus for his pet, thanks to Go For The Throat. Crit rocks and that's all there is to it. Crit-damage, pet-damage, it's all yummy. Unlike if we chose Armor Pen:
- Armor Pen can, and will, have its effectiveness immediately nerfed due to the warrior in the party throwing Sunder Armor
- The squishier the mob, the less effective our Armor Penetration will be
- Because we chose the Armor Pen-chest, we reduced our Crit by the amount we would've had, had we chosen the Crit-chest
Armor Penetration is not a bad stat, it's just the least-effective one we hunters have when we factor our party members interfering with our Armor Pen's efficiency. Adding Armor Penetration rating isn't a terrible thing, just remember to never sacrifice Agility or Ranged Attack Power or Crit to take Armor Pen.
And now you know why you should always look at your warriors with a crooked glance; they're in ur party, stealin' ur stats...