I have a pally I always planned on leveling up to be the tank for my shamans. I never really bothered with it though because the pally is only a fraction as useful for PvP as a 5th shaman would be (for world/bg pvp not arena).

Anyway now that DKs are here, I'm thinking they might have enough PvP utility to be good PvE tanks for 4 shamans but also contribute as much or MORE towards PvP than a 5th shaman.

Input? Comparisons? Compare the following 3 teams for PvE and PvP viability:

5 shamans
1 pally 4 shamans
1 DK 4 shamans