Something I do on the summoner guy is run to the top of the stairs, kill the mobs as they come to you, then the minute his shield drops run down and kill him. With druid heals I just heal throught the AoE.
Before doing it this way I had issues with him.
I also got DK last night on my second group (I have 2 other 80s I am running the daily with mixed back in with the main group), I had abotu 30 minutes to run DK so I did first boss and then skipped to the last boss to get my Frost Emblems, run took about 20 minutes