Three mistweavers will do tons of damage if you have the caster heirlooms (I found levelling mine that I was often 1st or 2nd dps in dungeons until Cata content). I would worry that on a full rotation you'll run oom because the 5.1 patch changes were pretty brutal on mana for everyone, including levelling monks. If you are running with more than one your rotations won't be tricky at all because eminence healing plus smart hotting yourself a few times a minute should be all you need (the hot spreads to the two lowest health targets). I levelled pre 5.1, though, so I'm not sure how nasty the mana nerfs are for levelling, I've heard they are pretty brutal.

If mana gets tight though, you can gate your rotation with glyphed mana teas to slow the mana spending.