If i understand it right you will have a choice between running dk+4 pallys or running with 5 pallys.

I think you can't go wrong with either grouping. The advantage to the DK is that it's already uncrittable,
which may get you hitting heroics on your group that bit quicker.

Then again the pally is a very, very capable multibox tank. Easy to macro.

It may come down to personal preference. Which do you prefer playing?