I agree with going unholy as the best-suited for multiboxing tank. Frost more for single-target/raid tanking. That being said, my DKs only at 65 atm and on a different team than my 5 shammies right now as I bring him up. So, caveat emptor. Unholy brings you the best AoE tools plus the epic Ebon Plaguebringer +12% spell damage (you DO have 4 shammies to unload that damage).

As far as builds, I'm thinking about foregoing Toughness in Tier One of the frost tree. A 15% armor boost comes out to about 3-4% additional damage mitigation at level 80 armor levels, against physical attacks only, for 5 talent points. Improved Frost Fever seems to be a much better deal - a 6% melee/ranged attacker slow down, for only 3 talent points.

I also just can't live without Unholy Aura. A 15% party movement speed bonus without the Aspect of the Dazed effect is just too sweet. Running my five shammies now is painful.

Here's my stab at a talent build. Probably the AMZ is of limited use in instances but I figure it will be helpful in PvP.

http://www.worldofwarcraft.com/info/...53121203133151