I used my 60 DK on RFC, after that I've started using my 70 mage. I will likely be going back to the DK soon as my Shamans are catching up to him. He is Unholy as well. I forget its name, but I have the talent that lets you keep the minion. So what I would do is gather everything up, cast DnD and then put pet on defensive and just let him go nuts. He ate them up pretty quick. I'm sure tactics change as the mobs get tougher, but spec'ing to keep the minion out to sick on the mobs after you AE them might be something to keep in mind.