I've always ran it as empathic healing, where the healer would take the wounds upon themselves and then heal the wounds using their base lists.
My favorite healer doubled as a beserker/fighter. Through judicious selection of talents, he was able to wield a war mattock (his one weapon) effectively, wear breastplates, and frenzy thanks to the healer's bonus to self control skills. He would wade into the melee and heal any damage he managed to sustain thanks to the healer base lists being subconscious.
The drawback of course was that being frenzied tended to hamper his ability to notice that his teammates might need some healing too. But it sure was fun.
A less aggressive healer would likely still be the MVP of the group. They would also tend to level up faster than most due to the constant spell casting and other skill checks that go along with the profession.