regarding DK tanking

In my expierence, a DK requires quite a lot of interaction. Keeping track of what runes are active, which abilities proc, possitioning is a bit harder etc. It's will be hard to figure out a good rotation that can work with the rest of your team, but not impossible. But one thing is sure, if you are able to pull it off to play with a DK tank, you just got yourself an extra dps'er in the team (seen some insane things in beta; 5-10k damage on each target within AE range). It's a path worth considering but certainly not the easymode the paladin offers these days.