DKs are pretty easymode. It depends on your play style, do you want to be up in your face or have the ability to switch to being a ranged team? Example, I was leveling my five shaman as enhancement and yesterday swapped back to elemental at 88. The elemental style allows me to spec swap into resto mode for 6 minute AVs with 2 tanks or what ever. DKs can't do that it is either frost spam or being blood and being slow killers.

There was a thread about a druid, 2-3 DKs and a shaman earlier. Shaman or DK are interchangeable but DKs give you death grip as opposed to being kited by mages/hunters. Pick your poison and play what makes you feel good.