Cross-posted from the "Rogues: Essential Class or Sacred Cow" thread:
The problem with literary models for the D&D cleric is that the role the class serves (glorified medic who provides healing and support but can also be a second-line fighter when necessary) is much more necessary in a game than in literature (where the author doesn't have to keep track of his protagonist's hp total). It's not hard to find saint/holy man/miracle-worker archetypes in myth and literature, but they don't look much like D&D clerics -- they aren't "adventurers," they don't fight, and they certainly don't go delving into dark caves looking for treasure. The knights hospitalers, St. Martin of Tours, Bishop Odo (depicted in the Bayeux tapestry), Archbishop Turpin (from the Song of Roland), Friar Tuck (perhaps) -- that's about it for fighting/"adventuring" holy men in myth/history, and significantly all of those are more post-hoc rationalizations for the D&D cleric class than archetypal models -- I find it hard to believe that anyone actually comes into the game thinking "I want to play someone like St. Martin of Tours" (which is also, presumably, why the cleric class is so famously unpopular among players, despite being overpowered (at least in AD&D and 3E)).
Therefore, I think the D&D cleric class is also a sacred cow that the game could survive without, at least archetypally. Mechanically you'd have to spread out the cleric's healing abilities to other characters -- include a first aid/chirurgery skill that anybody can use for "light" healing (hp recovery) and add an expert medic/surgeon class (mostly NPCs) who can perform more elaborate healing (cure blindness, disease, poison, re-attach severed limbs, etc.) and create healing potions and poultices; with that, the actual holy man class (ability vs. undead, resurrection and all of the other non-healing cleric spells) would become, essentially, a variant/specialty magic-user (i.e. without any assumed/inherent combat focus) and would have a much stronger and more familiar archetype. Somebody who wanted to play a "traditional D&D cleric" would do so by combining levels of fighter and holy man (and perhaps surgeon).