So rather than a Cleric we could have a Priest. Of course, this Priest could be good or evil. The Priest is medeocre at combat, but has a lot of spells that protect and assault against their foes (the forces of evil/good).
Instead of Sacrifice, taking a members death as your own, what about one where you accept a percentage of the damage your party members receive. eg. a hit to the Warrior does 80% to the Warrior and 20% to the Priest. Or one where a party member can tap the Priest's health to replenish their own.
Aura's would just be a light ability. You could activate one aura at a time and it would provide a small bonus, much like a low level Bless. But the Priest could also get involved in other ways to assist the party further with healing and protection spells.
I think the Priest should have fairly average health and little combat skill, requiring that they be protected so that they can continue to protect the rest of the party. It's a bit like "kill the commander" combat. If the Priest dies, you can kiss your chances of success goodbye!
