Hmm, I'd say a party should include:
A warlock. Absolutely. Possibly more than one. At least one should attempt to get into the Repentant warlock prestige class ASAP, so that they can generate at-will healing.
A paladin - on the condition that their lay-of-hands abilities refresh at level-gain. Otherwise, not really worth it.
A dragon shaman. Absolutely vital for their fast-healing aura. Even if their lay-of-hands does not refresh, they're a good choice.
Any class from ToB. Crusaders are probably the best choice, but the others are also quite good at this sort of thing. Perhaps count 'level gain' as a new encounter and allow maneuvers to be swapped/refreshed at that point.
Any class that can manage unlimited healing.
Also ranger, if they focus on one of the spell-less undead-slaying prestige classes.