I did the DK + 4 Rets. I found going Frost spec + Frost presence (for bonus HP and armor, people seem to like to focus the leader...) with the DK really plugged holes vs. just Paladins alone.

Howling Blast + Glyph of Howling Blast + Chilblains = massive AoE snare at 30 yards. Use Jamba for follow strobing, then just manauver your DK so your target stays between you and the Rets (easier with Chilblains). DG is great too, but HB is on a 8 sec CD.

And don't forget Imp Icy Talons and Horn of Winter.
Guess I`m stuck to frost them haha, did you take the blood selfheal with the your frost spec?

And maybe a stupid question but I`ve been wondering for a while now. What is this strobing?