Probably a Guardian - but the problem with them is that they have to level through catacombs if you only heal. Though I guess that's similar with all 100% healers...
But just make a guardian and put every stat point into intelligence then melee from 1 - 15 with clubs with enhanced effect and armour/charm with strength. At 15 I'd switch to using a heal mastery weapon/armour and get a heal charm. Then just upgrade your gear whenever you can afford it
