A bard is hands-down the best 5th party member in this situation, but only if things are done properly.
A human bard at 1st level can invest its feats in Precise Shot and Point Blank Shot, solidifying its future role as a missile weapon combatant only. Put your good stats in Dexterity, Charisma, and Intelligence (in that order) and pick a nice light suit of armor and consider a buckler. This gives you a fair AC and lots of mobility to run around firing arrows from your longbow (or shortbow if you're broke). Since you have precise shot, you can effectively double-team or triple-team opponents.
Since the bard has the missile weapon focus, the fighter should choose his feats down the path of becoming melee dominant. The Power Attack and Combat Expertise chains are the best bet, since one raises the damage potential while the other lets them cripple foes.
The rogue and the bard should work together on their skill choices so that they compliment each other. As the bard's Charisma is high due to spellcasting, things like Use Magic Device and Diplomacy should shift more towards him. Since he'll undoubtedly be more heavily armored, things with Armor Check Penalties should go towards the rogue. Minor overlap could be considered just in case one or the other is disabled at the time.
The cleric will be the dominant healer, but the bard can consider taking some minor healing spells for emergencies as well as always being well-stocked with cure spell wands, freeing up most of his spell slots. Remember, the bard is just a critical-situation healer.
What the bard should do, however, is focus on the enchantment and illusion spells, freeing the wizard up to take the evocation spells that blow stuff up real good.
Whenever the bard doesn't have a role, he should be using his music to improve the rest of the party.
This way, you have everyone in nice roles:
Fighter: Melee expert. Human shield. Monster killer.
Cleric: Healer, support spellcaster, backup melee character.
Rogue: Stealth, mobility, and detection skill focus.
Wizard: Combat spell focus with some support spells.
Bard: Ranged combatant, party face, emergency support in any role.