Melee teams without cleave, die rather quickly to any team with cleave (melee or spell).
My Ferals still don't like Demo Warlocks... that five boxer got the team three or four times in one match.

I think my DK's would do a lot better.
Mainly because they can each hit all five warlocks at the same time, instead of everyone dying as they kill one target.
Plus a healer outside of the AoE healing, cannot hurt.