Unholy bastards

All taken from:
http://elitistjerks.com/f72/t72364-unholy_dps_scourge_strike_neverending_dream/

* Superior Sustained AoE Dps

Unholy is, unarguably, the strongest spec in the game at this role. No one - caster or melee - can top an Unholy DK on any fight with significant AoE, not if the DK knows his stuff. The lead in this area isn't a matter of a couple percent (as is Blood's/Frost's single target dps lead on Unholy. That difference is smaller than ever before); it's quite significant (varying on the exact number of mobs - the more, the larger the gap becomes).

* Superior Raid Utility

Abomination's Might and Improved Icy Talons, although obviously excellent, can be provided by other classes and other specs with the exact same result. Ebon Plague, on the other hand, cannot. Warlocks and Moonkin cannot provide their magic damage debuffs on multiple targets at the same time - not without incredible hardship and the sacrifice of their entire personal dps. What more is that Ebon Plague does something no other class or spec in the game can do: It increases disease damage by 30% - a significant amount.
With diseases becoming increasingly important for all DKs, regardless of spec, thanks to the 15% damage boost they received in patch 3.2.0 and the 4p t9 set bonus, EP becomes increasingly valuable. If your raid contains at least two DKs, one being you, it is almost always worth it for one to go Unholy. Not only that, but with Devouring Plague being 10-15% of a shadow priest's damage, it's 3-5% more additional dps for them, with is essentially ~210-350 dps per spriest in your raid. EP is just huge. It cannot be stated enough.
* Superior Survivability

Bone Shield provides a near-passive 20% damage reduction. That's 20% less damage from every single AoE, every single nuke, every single add meleeing you - everything. It's highly underrated, but can be the difference between life and death in a million and one situations. Vampiric Blood and Unbreakable Armor, although excellent from a tank point of view, don't compare for dpsers.

Imp Unholy Presence 2H
- If you do not yet have 4p t9, you'll want to shift two points in Dark Conviction to Bladed Armor. Played in Unholy Presence, this build works the same way as its brethren. If your haste falls below a certain threshold (the exact number has yet to be identified, but it's somewhere in the 200-300 range), this spec pulls ahead of Blood Presence due to the GCD reduction - once you surpass that specific haste, as one does easily in CC gear, it becomes inferior and not worth speccing. The downside to using UP, even when you are undergeared and its worth the single target bump, is the AoE loss; yes, you can always just switch to Blood Presence for AoE fights, however what about fights where you AoE about half the time and single target the other half (which many AoE fights are actually like)? Switching presences in combat is going to lose you dps, but if you don't switch you are either stuck in blood (losing half the reason to be this spec) or stuck in unholy (losing a ton of AoE damage for little gain). Regardless, some find it worth the change. Your auto-attack will be the highest percent of your total damage, followed by your Ghoul and then your Death Coil. Death Coil plus it's subsequent UB will be your hardest hitting individual ability, followed closely by Scourge Strike.
14/0/57

Optional Talents
Although none of the specs (with the exception of Blood Presence DW) have free floating points to spend on whatever you choose, one can take points from either Bladed Armor or Dark Conviction at a relatively minor dps loss in favor of the utility provided by other talents:


* Ghoul Frenzy – This talent should only be taken if you have trouble keeping your Ghoul alive. If you do, it becomes invaluable, as a dead Ghoul is a large portion of your dps down the drain (due to 30 seconds of absolutely zero Ghoul damage, followed by your Ghoul doing reduced damage for the remainder of the fight from missing buffs). If you don’t have issues with your Ghoul going down, then skip this talent. In nearly every case it will be a dps loss.


* Improved Unholy Presence – Already taken in the Unholy Presence builds, Improved Unholy Presence is occasionally taken in Blood Presence builds solely for the runspeed increase, which some consider worth the sacrifice. How much of a dps boost the run speed increase itself is is very difficult to calculate. The value varies drastically from fight to fight. The best option to determine its worth is to try it out yourself, see if you notice a difference and, if you do, decide whether or not it is worth the two talent point. There is no right and wrong answer as to whether or not you should spec into IUP.


* Epidemic - As already discussed, this talent is no longer worth the points from a single target point of view. From an AoE perspective, you do lose out however, and as such some still consider it a must have, even if the AoE loss is ever so slight.

Glyphs
Major

* [Glyph of Dark Death]
* [Glyph of the Ghoul]
* [Glyph of Icy Touch]

Minor

* [Glyph of Horn of Winter]
* [Glyph of Pestilence]
* [Glyph of Raise Dead]

Spell rotation
Single target
IT – PS – SS – BS – BS – DC – (HoW) – DC
IT – PS – SS – BS – BS – DC – DC

Multi target
IT – PS – Pestilence – DnD – DC – HoW
IT – PS – Pestilence – BS – SS – DC – DC

Gear Wise Unholy Dks are difficult to weigh up upgrades.

But generally its Strength is prio as ever, never gem for attack power, because it doesnt scale with your weapon enchant, nor does it buff with kings (unless they've changed kings).

Crit comes a very close second.

Armour pen, hit and haste all have roughly the same importance.

On the elitist forumn, theres a very difficult gear weight ratio that I cant be bothered to add up. the Values are as follows for those who are interested.


IUP = Imp. Unholy Presense

Stats BP Builds	IUP	Builds
Attack Power	1.0	1.0
Weapon Speed	238.10	112.9
Weapon DPS	6.03	6.13
Hit Rating (untill cap)	3.05	1.97
Strength	3.05	3.10
Haste	2.19	1.29
Crit Rating w/ 4pt9	2.19	2.00
Expertise Rating	1.65	0.45
Crit Rating	1.60	1.50
Hit Rating till spell cap	1.40	0.93
Armour Pen	1.30	1.29
Agility	1.05	1.00

Taking Advantage of AMS

Ignored or forgotten by many, Anti-Magic Shell not only absorbs magic damage, it also produces Runic Power based on the damage absorbed. More Runic Power translates directly into more damage and, as such, the proper use of AMS is a skill essential for a DK wishing to perform to their very best. Darkside did an excellent job of explaining this for Frost DKs and, as such, most of this is a reprint of his comments - with his permission, of course.

unholy dk's really are masters of aoe dps. but you forgot blood boil into that rotation. it hits every mob in range and is increased 12.5% per desease.

i have just lost my 4 piece t9 bonus due to upgraded gear, so will see whether or not i lose out dps wise. time will tell.