Lots of guides on what particular aspect of the unholy tree you should or should not keep. Do you keep your ghoul? Do you get morbidity? What about AMZ? Or do you just stick with Magic Suppression?
You could do a search on the internet and find a zillion and ten different specs and people clamoring as to why their spec works the best.
Let's go over the basics though, shall we?
One of the key components of an unholy tank is Bone Shield. This ability is on a 1 minute cooldown and comes with a base of 4 bones. Glyphed and you have 6 bones.
While this shield is active, we take 20% less damage and do 2% more damage. The more damage stuff is why Unholy DPS keep it up, even though they hopefully aren't taking damage, but the 20% reduction is what we're after.
Frost is considered "the" tank spec for Death Knights because it contains a lot of really nice damage mitigation abilities. Of which I care nothing for, since I'm not Frost. Go somewhere else to read about why a lot of DK tanks are Frost.
We unholy DK's however, we love our Bone Shield. The more we parry, the longer Bone Shield sticks around. The ideal is you want to pop your shield so it's cooled down before you even go in to touch a boss.
With the idea that Bone Shield is our baby and we want to preserve as much of it as we can until the next cooldown, a high dodge and parry becomes not just 'well, duh' abilities for us, it becomes essential for us to try to keep our dodge and parry as high as possible so when we do get hit, we take 20% less damage.
Because of that, one of the 'basic' abilities is Blade Barrier. The hard part for us is keeping those runes on cooldown. The DPS version of our rotation is heavy on Scourge Strikes. The tank version of our rotation is initially heavy on Blood Strike. We want to have Blade Barrier go off as soon as possible, and we want to KEEP those runes on cooldown as best we can to keep the barrier up, especially if our shield goes bye bye.
One of the things that will swiftly make your shield go away is if a mob gets behind you. You can't parry attacks coming at your ass, if you recall.
With our lack of physical shields, it's also imperative to take Toughness in the first tier of Frost.
And then it seems a no-brainer to also take Anticipation in the first tier of Unholy.
Now, these three are the 'basic' abilities that most DK tanks are recommended to start with. Given that our only way of avoiding incoming damage is armor, dodge and parry... it seems sensible (thank you Blizzard) that all three talents are in the first tier of the trees.
Each particular brand of tank, Frost, Blood and Unholy, have their own particular ideas about how to mitigate damage and what they should spec in. I'm only talking about Unholy here. I have not played a Frost or Blood DeathKnight and I won't entertain the idea that I can tell one how to play anymore than I'd feel comfortable trying to tell a Destruction or Demonology warlock how to play.
In my opinion... whatever spec you pick, whatever talents you take, if you can live through most things with your average healer, then you're doing something right. Some things may just make that easier than others. As Unholy, you've already decided to not go the 'usual' tanking route of Frost, Blood, or Frost/Blood hybrid.
My current rotation is opening up with Death and Decay (1B1F1U), Icy Touch (1F), Plague Strike (1U) and then Pestilence (1B)... and then Blood Boil (1B) / Blood Strike (1B) as soon as a rune goes off cooldown. The nice thing about Pestilence + Blood Boil is that it helps sink the aggro of all the things you may be tanking onto you.
As soon as you have the runic power for it, hit Unholy Blight, the other keystone ability that Unholy Tanks chortle over. It costs 40 Runic Power, so it isn't something that we can often hit right away. However, just like the Pestilence/BloodBoil combo, this is another handy trick that we can use to AoE tank (and do lots of damage, nummy nummy damage).
Some arguable no-no's:
- Corpse Explosion: While it sounds really nice as another way of sinking aggro on multiple mobs, you'll probably not have the runic power to spare, keeping up Unholy Blight as you will be.
- Desecration: This one is very arguable, often DPS will open up before you've had a chance to really sink your initial AoE aggro in, and if you put points into Desecration, the mobs may not run off so quickly before you can get it back. DPS usually only put about 3 points into this ability, but if you take it for tanking, you may consider 5/5 to guarantee your first Plague Strike will kick this puppy into gear.
- Blood-Caked Blade: Reports of this is that it has a separate miss/hit/parry attack than your actual melee attack, so each swing has two chances for you to get parried. We've discussed the parry issue before.
- Outbreak: Another argued ability. Plague Strike still does a good deal of damage, especially if you have the Glyph for it, and we've already discussed Blood Boil. But is it really needed for tanking? (I have it, personally.)
- Master of Ghouls: A lot of Unholy Tanks will give up their pet. I'm of two minds on it just yet. Right now, he's gone. That may change if I feel that having my pet out for extra damage will be more beneficial than having to worry about keeping my pet alive. Having one available for Death Pact is a BIIIIG bonus in my head.
Some arguable yes please!
- Virulence: Surprisingly, Unholy DK's have a higher hit cap than you'd imagine. You say to yourself, well, unless you're dual wielding, it's 9%, right? ... sort of. We actually do quite a bit of magic damage and so our magic hit cap is actually 17%, right up there with the casters.
- Magic Supression: A shield that will eat a bunch of magic damage? Yes plz.
- Ebon Plaguebringer: Makes them suseptible to magic and does more damage for diseases, basically a party debuff. It makes your casters give you kisses.
- Improved Icy Touch: This is a Frost ability, but some Unholy tanks will take the option for it.
- Bladed Armor: Yum, attack power! Some people pass this over in favor of the following.
- Two-Handed Weapon Specialization: More dmg! More dmg! Some people pass this over in favor of the previous.
- Ravenous Dead: Anything that increases our strength can't be bad, even if we don't have a pet all the time!
- Shadow of Death: While we may or may not have a pet out, again increasing strength and stamina is good!
- I'll toss Master of Ghouls down here too, because I'm honestly not sure if it's a 'not worth it', or a 'worth it'. I'm leaning towards worth it and thinking I can drop a point in Outbreak to get it again.
Other basics: 540 is the defense you're looking for to be uncrittable to mobs three levels higher than you. 535 is the recommended 'minimum' for tanking heroics, though a lot of tanks go in there with less as they work on their gear.
Where to find defense gear is another problem! We don't have shields, which usually stack some defense and health onto them. Instead, we have to deal with drops or crafted gear. You can easily hit uncrittable (or very very close to it) and close to 19k health with the crafted Tempered Saronite gear plus crafted Daunting gear, the Stoneguard Band (crafted JC) and of course, Rune of the Stoneskin Gargoyle. A good easy cloak to get is the Cloak of Peaceful Resolutions from Honored-Wyrmrest. Toss on some enchants onto those pieces, practice your rotations and keeping blade barrier active and voila, insta-tank!
In terms of what stats to stack, obviously stamina is an important one, but please do NOT overlook Strength. 25% of our strength is added to our parry rating. Naturally, hit and expertise are important too, but becoming uncrittable and maintaining a high parry and dodge rating should be what you focus on first.