Hunters would be super easy to level, and not a bad way to get your feet wet as far as WoW goes. it seems to me that if you are leveling with the intention of boosting up other characters with your level 70 i am not sure the Hunter(s) would be optimal {Correct me if I am wrong all}... I could be completely off base though since my experience with level 70 hunters is limited to getting blown up by them.

When I switched from EQ to WoW I started off by going with a healer+other combo for a duoing, but that's mostly due to duoing a cleric + war in EQ for years and years and years... i just became very accustomed to having that pocket healer. The biggest "gotcha" that I had when switching over was the pace of combat and just overall timing mechanics, once you get used to the subtle differences you will find that there is very little difference between multi-boxing either game.