Now we get to it, you say?
Gief me Purplz!!!
It's all about the loot.
As a raider, however, you should know what loot will help you be the best dps DK you can be, and what gear will get people whispering about the Deathtard in spell power plate.
Going APE: selecting gear for maximal raid effectiveness.
"I have the Helm of Zygranar, should I roll on the Hat of Hitting Hard?"
Most raiders use a gear rating system to determine what gear will maximize their effectiveness.
This system is commonly referred to as APE: Attack Power Equivalence. Attack Power (AP) is the stat used to calculate the damage each of your abilities does and is therefore a nice measuring stick for what other stats have more or less value. Not all stats are created equal!
AP = 1 APE.
That being said, it can be difficult to determine whether crit is better than haste, especially given that the answer depends on your spec and raid buffs.
A few basic comments, and then I'll list the 'current' APE values for each spec.
Strength = 2 AP. This means that you'll get two attack power for every strength. Strength is usually worth more than 2 APE however, because the raid buff Blessing of Kings adds 10% more strength AND 10% more agility, while raid AP buffs add a flat amount. In addition, your pets will scale with strength better than ap (especially ghoul).
Crit. Obviously, increases the percentage chance of getting a critical hit. For DKs crit is good because it doubles the damage of the attack, and many DK talents increase the damage of a crit even more.
Haste. Increases speed of white attacks. Doesn't increase rune cooldowns, so doesn't do much for special (yellow) attacks.
Armor Penetration. Raid bosses have lots of armor, which mitigates physical damage. Arpen for DKs varies depending how how much of your damage is physical (Blood is the most, unholy the least - changing for 3.3).
Agility. Agility increases crit chance.
Expertise. Decreases chance to be parried or dodged. In most cases, we should be dpsing from behind, so dodge is what we're concerned about.
Hit. Decreases chance to miss the target (you have a built-in chance to miss based on the boss' level and your 'natural tendency' to miss if your hit = 0).
Weapon DPS. The dps rating on the weapon. Speed matters somewhat but I won't get into it. Slower is better.
In terms of DPS, these are the only stats of value! The only other thing that contributes anything to dps is armor if you have the talent bladed armor, but armor rating is entirely tied or ilevel and therefore not something you'll make gear selections about. Stam is nice, and can keep you alive, but it has no APE value. Spell power, Int, Spell Penetration, and so on, have no value for PVE.
APE values are derived in two ways. First, they can generally be theorycrafted by calculating what each stat will do for each type of attack. The second is by running gear sets (with known stats) through a simulator. Both have been done extensively by theorycrafters at EJ and elsewhere. While they don't always come up with the same results, generally the numbers I'll present here are in the ball park of what's accepted.
With no further ado: 3.2.2 APE values by spec.
AP = 1
Strength = 2.89
Hit = 2.51 to hit cap (about 262)/ 0.52 after: I don't value hit very high in gear calculations because it's so easy to get.
Armor Penetration = 2.4
Expertise = 2.47
Crit = 1.56
Agility = 1.37
Haste = 1.5
DPS = 9.89
AP = 1
Str = 2.68
Hit = 3.52 before cap/ .99 after
Arpen = 1.58
Exp = 2.97
Crit = 1.84
Agi = 1.42
Haste = 1.26
DPS = 6.77
AP = 1
Str = 3.05
Hit = 3.05 before cap/ 1.4 after
Arpen = 1.3
Exp = 1.65
Crit = 2.19
Agi = 1.05
Haste = 2.19
DPS = 6.03
As you can see, while there are similarities across the board, some specs value certain stats more than others.
If you want help sorting all this out, there are a number of sites that can help. Lootrank.com is a very popular one, as is Maxdps. I mentioned the two sims and Rawr in my previous posts. There are other dk gear optimizers as well. They can be very helpful. Some of them let you put in your own APE, while others don't.
I've found, however, that none of them end up giving me the exact results I'm looking for. So, I use them as a starting point and then make my own decisions.
I've even done my own Excel spreadsheets to put in my own item lists, statweights, and then done my own number crunching. I don't have a nice way of uploading them at the moment, but if you are interested in my personal spreadsheets, drop me a line and I'd be happy to pm/email them to you.
Happy hunting, and go get that DK decked out!