They do have a Healer, the Druid. Vigor makes him better than the Cleric at that.

@The OP:My favorite caster for simplicity, usefulness, and fun is the Beguiler. You literally can't make bad decisions while building them, just put everything into Int and you're good. It's non-core, but one of the group might have access. Spontaneous casting from a pre-chosen list with very good spells on it, light armor, and 6+Int skills give you a lot more options than a standard Sorcerer and it's a lot easier than picking up a Wizard for the first time. Pretty much, it's Arcane Trickster out of the box.