One of the commonest complaints leveled against the cleric is that the class is just a glorified healer and nobody likes to play the healer. I have to admit that I've always been puzzled by this assertion, because in my experience, while cleric is indeed a healing class, that's not all that it is. Yet, you'll still hear lots of people make the baseless assertion, for example, that the reason the cleric was included in OD&D is because of the need for magical healing. I call this assertion baseless, because Chainmail, whose fantasy supplement is the immediate precursor to OD&D, does not include clerics among the options for play. There are "heroes," "superheroes," (both examples of what would later be called fighting men or fighters) and wizards, but no clerics. So where did clerics come from?
Like many things from the prehistory of roleplaying, the answer to this question is murky, but the most consistent explanation and the one offered by Mike "Old Geezer" Mornard, who enjoys the possibly unique distinction having played in the campaigns of Dave Arneson, Gary Gygax, and M.A.R. Barker. According to Mornard, Dave Arneson created the cleric class, modeling him on Abraham van Helsing as portrayed by Peter Cushing's portrayal of the vampire hunter in the Hammer Films series. According to this version, the cleric was intended as a foil to a vampire player character in Arneson's campaign, Sir Fang by name, meaning that the class was first and foremost conceived as a fighter of the undead, a role it has retained throughout every edition, including 4e.
As presented in OD&D, a cleric can heal. However, of the 26 clerical spells offered in the little brown books, only two -- cure light wounds and cure serious wounds -- are direct healing spells. Supplement I expands the total number of clerical spells to 46, but adds no more healing spells. There were, of course, "restorative" spells of various sorts, such as remove curse (which the cleric shared with the magic-user) and cure disease, as well as neutralize poison and raise dead. Nevertheless, the bulk of the cleric's spell selection in OD&D is made up of what might best be called "utility" spells -- light (again, shared with the MU), find traps, locate object, speak with plants, create food, word of recall, control weather, and so on.
AD&D expands the spell list for clerics yet again. There are 76 cleric spells in First Edition. Of these, there are only two new direct healing spells -- cure critical wounds and heal. The majority of the new spells are additional utility spells, particularly abjurations and divinations. Second Edition follows First quite closely in most respects, but the addition of specialty priests (of which the traditional mace-wielding cleric is but one possible example) actually made it possible to play a "cleric" who couldn't heal at all. Third Edition adds many, many more spells to the cleric's repertoire, including some new direct healing spells to fill in gaps in the progression (cure moderate wounds, for example), but, again, the vast majority of a cleric's spells are utility spells. Moreover, 3e seems to have gone out of its way to ensure there were also direct damage-dealing options available to clerics, a category that was largely non-existent in previous editions. Of course, 3e also added the spontaneous casting of healing spells, which allowed a cleric to freely convert any spell into a healing spell of the same level. Thus, if any edition formally turned the cleric into the "medic," it was 3e, but, even there, the charge is weak. (As an aside, in OD&D, evil clerics -- called "anti-clerics" -- could not heal at all and cast damage-dealing spells instead)
The identification of the cleric with "healer" is a classic example of how game rules sometimes take on a life of their own through play. Because the cleric was initially the only character class who could heal at all, that ability soon became its singular distinction. OD&D describes clerics in terms that suggest it was intended to be a "hybrid" between the fighting man and the magic-user. Likewise, AD&D -- and Gygax himself -- makes a connection between clerics and the medieval orders of religious knighthood, like the Templars. Thus, they were intended to be religious militants: crusaders who went toe to toe with their enemies rather than standing in the back and healing, to borrow a MMO turn of phrase. Part of the problem is that, in AD&D, the paladin usurped that role (OD&D's paladin is a slightly different class -- it's not a spellcaster, for one), leaving the cleric holding the medkit. The other issue is that, except during the 2e era, D&D has never provided examples of non-clerical "priests," which is to say, religious leaders who tended to the needs of the faithful. That made it hard to make a distinction between adventuring clerics who bashed skulls for their gods and the parish priests who hung around Hommlet preaching and giving alms.
Unfortunately, the D&D cleric is an incoherent mess -- half what its creators intended it to be and half what players expect it to be. I can't in good conscience recommend ditching either half, because the tension between the two is part of what makes the cleric what it is. On the other hand, I'm completely sympathetic to the notion that the cleric is in need of something; I'm just not sure what that is. In any pulp fantasy game I write, I'd be inclined to ditch the cleric entirely or subsume most of his abilities into an expanded magic-user class. That seems truer to the source material. But if I were doing anything that had to be recognizable as "D&D," I don't quite know what I'd do. Moreso than any other class, the cleric has issues that aren't easily resolvable and pretty much any proposed solution is sure to tick someone off.