As this fine answer mentions, there's absolutely nothing wrong with the dnd-3.5e cleric… it really is one of the game's most powerful and versatile classes, the designers perhaps overcompensating for the stigma of cleric-as-healbot in adnd and, to a lesser degree, in adnd-2e. The power comes from being a full caster with eventual access to 9th-level spells, and the versatility comes from being able to draw from any of the game's second largest list of spells and picking new spells to prepare each day. These plus the cleric's domains, the ability to turn undead (the utility of which expands vastly outside the core rules), variant class options, and prestige class options make the cleric tier 1. A cleric is easily the wizard's divine counterpart, the wizard's combat equal and—arguably—support superior. And if getting power from the gods is a concern, skip that jazz and be empowered by the strength of your convictions, worshiping no god at all.
Anyone can heal…
In a traditional campaign, a potion of cure light wounds [conj] (PH 215-6) (1st-level spell at caster level 1) (DMG 230) (50 gp; 0.1 lbs.) is typically within a starting PC's budget and more such potions are available in any town with a population greater than 80.
With 750 gp in your pocket, a wand of cure light wounds [conj] (PH 215-6) (1st-level spell at caster level 1) (DMG 246) (15 gp/charge; 0 lbs.) becomes available, and that's sufficient for healing the entire party after each encounter for at least one level, sometimes two. A level 1 bard, paladin, and ranger can use such a wand as effectively as a cleric can, and anyone with a Use Magic Device skill modifier of at least +2 can probably use such a wand a couple of times before having to set it aside for the next day. That same amount of cash also buys a healing belt (Magic Item Compendium 110) (750 gp; 1 lb.) that's pretty close to 6 cure light wounds spells per day forever and that anyone can use… even the fighter. Both, by the way, are available in a town with a population of at least 901. (Yes, the Dungeon Master's Guide really is that specific!)
In other words, you don't need a healer. A cure light wounds spell, while sometimes useful in a pinch, is usually a waste of actions in combat. That is, it's usually better to just kill the dude who's trying to kill you than fix your friend who'll die by the dude's sword next round anyway—the amount of damage healing fixes is usually markedly less than the enemy can deal. Keep on hand a blessed bandage (Magic Item Compendium 152-3) (10 gp; 0 lbs.) or two in case allies needs to be stabilized.
Should someone be able to heal the party when combat ends? Sure. But at level 1, that's not happening anyway; that's called resting. And by level 2 by pooling your cash, a bard can do that end-of-combat healing instead… or one of the bruisers can, who'll likely look at that second or third level of fighter or barbarian and say, "Hey, a level of ranger or paladin would be pretty awesome right about now."
…And support? There's already a bard!
Further, with a group of six—the game's designed for groups of four—that bard's become a serious force multiplier. (That is, unless, of course, he hasn't… a bard can take alternative class features that make him more—let's say—selfish, but such bards are rare.) The bard's inspire courage overlaps with the 1st-level Clr spell bless [ench] (PH 205) anyway, and a cleric doesn't get better than that spell for mass support until the 3rd-level Clr spell prayer [ench] (PH 264), and I've honestly never seen a PC cast that spell. Further, while a level 1 cleric can buff other folks individually, he's often better off buffing himself then beating the crap out of things with his morningstar. And, of course, the best character to support the cleric in administering that beating is the bard.
Play what you want!
KRyan makes some fine alternative suggestions for a healer in this answer. I'm hesitant to suggest serious out-of-the-box alternatives that are completely not healers like incarnate and totemist (both of which I've played and had a great deal of fun with) from Magic of Incarnum or binder (one of my players has consistently—almost accidentally—ended up playing a binder in the past few campaigns) from Tome of Magic because such classes rely on otherwise unique subsystems that the DM may be unfamiliar with; however, all three are weird, and you can rest assured that you're not duplicating—precisely, anyway—the abilities possessed by the rest of the party. (I'd like to note that it's weird to ban psionics from an Arcanis campaign—Paradigm Concepts released Psionics Unbound specifically for the Arcanis setting!)
So instead of making hard suggestions, I suggest talking to the DM and learning what the campaign will be about—see if there are themes or ideas that will be explored, organizations that the PCs will interact with, regions you'll be traveling in, and so on that can guide your decision as to what class (or race or religion) to play. You might end up as a cleric/crusader/ruby knight vindicator or bard/war weaver/sublime chord anyway, but fitting in is important, too, and with five PCs already on the board, differentiating yourself that way may be a better route than trying to do so through your class choices, especially as a new entrant to the system.
