Blood tanking is by far the best until you can get enough effective health and avoidance to go unholy. The extra armor from UA doesn't help against magic based attacks, which a lot of bosses have. Once you get 4pt9 you can have it up for 15 seconds then only have to wait ~35 seconds til its back up. I find that far more beneficial and verasital then the extra armor.
http://www.wowarmory.com/character-s...yxia&n=Cirayne
EDIT: I have no problem holding threat on Single Target or AoE Targets. DnD, Heart Strike, Pestilence, Blood Boil, and ZOMG being a smart tank and hitting tab to white hit other targets never fails.