So how easy is it to tank Drak'Theron Keep as unholy? This easy.
Here was my build. As you can see, it's pretty easy to hold AOE agro as unholy, which is the way I like it.
I absolutely hate single target pulling, as it seems to make instances drag on for way longer than necessary. That's why I love to tank as unholy. So many juicy AOE talents. Unfortunately, Corpse Explosion is bugged and wouldn't let me use it on nearby undead corpses via auto target, and manually targeting corpses with 7 mobs in your face is a pain in the ass.
Overall I like it a lot. I had about 12% parry, 8% dodge, 16k armor, and 3 oh shit buttons with Lichborne, IBF, and Bone armor.
Combine that way multiple ways to grab and hold onto AOE agro, and instances get cleared very quickly.
Also I might note: I was doing roughly 1500 DPS the entire instance, while in frost presence. Granted, that probably has to do with the hunter serpent sting bug (targets take a ton more damage with serpent sting up right now for some reason). However, I was still #1 on damage with another 77 DK who was blood, a 75 hunter, and a 76 warlock with me. The paladin was holy.
It's also quite possibly the most gorgeous instance in the game thus far.
The music you hear is just some of Matt Uelmen's work from Naxx. Too bad he's no longer with the company. :/
Edit: Forgot to mention something. I tanked this instance using full green/blue DPS gear. Not one piece of defense gear was used. =]