I like the Paladin healer for two huge reasons (the rest is dressing):

1. Bubble. You bubble as soon as they focus on you and your DK's are tearing people up while they're wasting time.

2. Throughput with clickies. The amount of healing you can push out when you blow cooldowns is insane.

My wife has friends over, but once they're gone I'm going to record my DK manifesto and post it here on the site.