Like i said, best bet is to target a warlock.
http://www.wowhead.com/spell=62618 is not going to be good for melee teams.
with 4 dk + 1 healer, and dks last long enough to down the target with healing of their own is possible. Basically, put the other side's healer behind on healing, and you kill your target slowly. This is very possible. But if you leave the other 4 targets free for too long, they start to CC your healer + your DKs.
and
I just assume there is no prod. If there is, ignore him and kill others.