Is Armor Pen Worth it? What about Sunders? Haste? Strength? What do I gem?

Ok, so I did a little calculation, and here's what I can say about these things.

First the part that you can find many other places.

It is widely accepted that bosses in LK have been adjusted to all have 13083 armor value. GC also announced exactly how armor penetration is calculated, and I gave a few statements toward that earlier.

So, here's the skinny:

BASE:

Boss level = 83, boss armor = 13083, boss physical damage mitigation = 46.2%.

this means that out of every 100 points of damage you do, 53.8 points "get through" armor.

Before we look at armor penetration, let's look at sunders/faerie fire.

a 5 stack of sunders and FF give 25% reduction to armor value, which gives:

Boss level = 83, boss armor (minus Sx5/FF) = 9812, boss physical damage mitigation = 39.18%.

this means that out of every 100 points of damage you do, 60.82 get through. So, for classes with all physical damage output, that's a flat 13% dps increase. Sure, it takes some maintenance during the fight, but it stay's up pretty much the whole time, and it's raidwide.

Ok, now what does 100% armor penetration do for us?

Well, calculating the value using GC's formulas shows that for bosses

C = 400 + 85*(Lvl) + 4.5*85*(Lvl - 59)

or

C = 16635.

So, summing this with the armor value and dividing by 3 gives us the armor pen "effective armor" value of

(16635+13083)/3 = 9906

So, 100% armor penetration (no sunders) gives us:

Boss level = 83, Effective Armor (minus 100% ArP)=3177, Phys Damage mitigation = 17.26%.

so now, out of every 100 points of physical damage dealt, 82.74 get through, or an increase over the base of 55.6%.

I.e. for us, this means a flat out 55.6% dps increase without changing anything about our rotation.

Now, with sunders.

The calculation above is taken based on boss armor value, which is decreased by sunders and FF, so if we take these into account, remember the boss's armor value is reduced to 9812. So now the ArP cap becomes

(16635+9812)/3 = 8815.

So,

Boss Level = 83, Effective Armor = 997 (yep, that's all), Phys. Damage Mit. = 6.14%.

So, now, out of every 100 points of damage dealt, 93.86 get through. That's an increase over the baseline of 74.4%, and an increase of 13.4% over 100% armor penetration alone.

Now, as to whether or not this is worth going for is difficult to determine. Percentage increases for armor penetration are just as confusing as percentage increases, say, in critical strike. However, it's fair to say that a 1% increase in dps is the same either way. Especially if they stack, as these do. Notice, however, that a 1% increase in critical strike costs 46 crit rating points, while a 1% increase in armor pen costs 14. Admittedly, 1% armor penetration is really only about a half a point dps increase, but even looking at the scenario above, the price is still only about 25 armor pen for a 1% dps increase.

Strength, the other popular choice for gems, is a linear increase, and as such, benefits more the person who doesn't already have high dps. Each 20 points of Strength yield 40 Attack power, which add 2.86 dps onto your weapon stats, and if those scale with abilities, it adds to there too. However, many of our abilities use weapon damage and only use portions of our Attack Power to calculate damage dealt. Notice that if you're doing, let's say a respectable 5K dps in raids, 3 dps is adding a tiny fractional increase to your overall dps.

However, the combination of all of these seems to be the most effective. High strength/crit when possible, ArP until you hit cap, then your doing the following:

(DPS + Str)*Crit*Arp

That way you're getting the most out of all three.

If, for example, you have a 40% crit rating along with the 100% ArP and sunders, you're looking at a calculation like:

(DPS + Str)*(1.4)*(1.74) = 2.436*(DPS + Str)

Which should be doing an awful lot for your dps, I would think.

Compare that to either of the other possibilities:

(DPS + LOTS_Str) = DPS + Str + Extra Str

or

(DPS + Str)*(1.6) = 1.6*(DPS + Str)

around the point of crit diminishing returns

or even

(DPS + LOTS_Str)*(1.6) = 1.6*(DPS + Str) + 1.6*(Extra Str)

You can see that the higher your baseline DPS, the better benefit you get from using multiplicative stats over linear stats. If Haste actually affected your dps similarly, I'd end up going with a ArP + Crit + Haste model, but Haste only affects your swing speed, and your melee white damage typically hits about 12% of your overall dps, so if Haste speeds up your white swings by 100% (3279 haste rating, by the way) it would mean a 12% increase to your total dps, this is why warriors typically frown on haste in general. Supposedly in Cataclysm they're modifying how haste works for melee in some way to try to make it more attractive, but I'll have to wait to see. Since our attacks are primarily either instant, or (like Slam) on a specific swing timer that doesn't adjust (and this is not something that would really benefit a lot from needing massive amounts of haste rating) I'm not sure how they're planning on monkeying with our haste<-> rage conversions, but I'm keeping an open mind.

So, at the moment, my advice (take it for whatever it's worth) is to consider your stat priorities as follows:

Hit rating (minimum 164) try for 230-"ish"

Expertise soft cap at 214 rating.

Armor Penetration hard cap at 1400.

And whatever else you can afford, dump into some combination of critical strike and Strength.

Since Crit seems to hit a wall at about 60% (with raid buffs), I suspect that if your crit is already in the 45-50% range, you probably want to do more Strength.

And it is possible to do all of these, see my earlier post for examples.