My concern would be single target incoming damage. Seems to me a boss would methodically squash the DKs one by one.

Come to think of it though, anyone got a meter that tracks incoming damage? It occurs to me I have no idea how much healing is needed for any particular encounter. For all I know 3-6k HPS might be enough for 25 mans. (Again, i have no idea)

I guess if you want to get really fancy, you could rotate groups to get 8% max HP/sec with rune tap, add that on to 3k HPS from Blood Aura, that's anywhere from 18-23% max health restored every second on a central tank character, while maintaing aproximately 10-15% HPS for the rest of the raid.

Edit: Dammit, now I've got to Theorycraft this again.