There is a "trick" to this fight which lets you 1 tank it -- a DK, if they pop AntiMagicShell (AMS) while he is casting Whiteout, will not get affected by Whiteout. So you pop it during the 2nd cast of Whiteout, and you drop back to 1 stack. Same thing again on the 4th stack, etc to enrage.

So in theory you could take a mostly DK team in and keep going till enrage, you could even make them all (except tank) unholy and put pets on the orbs along with diseases.

Anyways I doubt anyone has 6-7 DKs and it would be kinda dumb from a loot point, but just fyi. If you are trying to 10 box it you can go with a single tank if that tank is a geared DK. You have to time AMS perfectly though, cast it during his cast of Whiteout but not too early since you need it on when it hits.