Okay, now remember, this is just my personal opinion on the matter. I have tried a frost tanking build, a few different blood tanking builds, and found them all useful. However, last night, after some thought and some research, I decided it was time to switch to an Unholy spec. Now, I tried unholy before, but I had specced into master of ghouls, and it made me feel like a hunter. I had to take a long shower after that.
I like Death and Decay, and the extra damage from that, and Desecration, seem like they will help me build some AoE threat, which for some reason, perhaps because I'm brand new at tanking, I was having trouble with as a blood tank.
Opinions, criticisms, and suggestions are all welcome, encouraged, and asked for. Don't hesitate to break my little heart, but so far this spec seems to work, although I haven't run an instance yet.
http://www.wowarmory.com/character-sheet.xml?r=Muradin&n=Vyrae