A friend of mine just started dual-boxing with RAF today (doh! forgot to refer him so I could level on one of my accounts with him!), and he's playing a rogue/druid. It's probably my 2nd favorite duo, just behind a paladin/mage.

I've run a couple teams that were all melee (working on all DKs now), and it's not bad at all once you just get used to it. I don't like spec'ing with skills that require positioning (combat rogues are great!), so that becomes a non-issue. The main thing is to keep them grouped close so they're all swinging at the same target.. mobs drop quick. I had considered a paladin/4xrogue team at one point, but switched to 5x rogues. The shaman/4x arms-warrior team was a lot of fun until Bliz changed windfury totem... :/

Now the 5x DKs are the "meat blender" team.