Just my $.02 paladins aren't the very best multiboxing healers. The trouble I had was no AoE heals so it I had to focus more on healing and it got to be a pain. I highly recommend a shadow priest and a boomkin (or resto druid). I am currently working towards:

Pally tank
Shadow Priest
Fire Mage
Resto Shaman
Affliction Lock

This is my 2nd group + my 10 man group. This team is currently 63, 70, 70, 59 and 69 respectively. I REALLY wish I had leveled a drood, but oh well :/