How to fix this party by adding one character (Pathfinder)

[Amurion]

We are starting out n a traditional dungeon crawl. We are all level six with 6000 starting gold. The party is composed of a human paladin, a dwarven barbarian, a half-orc fighter, and a bard4/gunslinger 2 (think Indiana Jones). I have my character to built and can't decide if a rogue, witch, cleric, or wizard would be better.

Any thoughts how to rebalance this party or should I just throw another melee or ranged beast in the mix?

[gartius]

it does seem you are a little light on battlefield control. Cleric or wizard would be best this depends on preference wizard can buff the party (everyone will love a haste from a wizard) or cleric for the healz-just make sure this is not the main focus of the character.

[StreamOfTheSky]

Definitely need a primary caster. Paladin can't handle healing that well, but at least it's something.

I'd probably do a wizard or witch.

How would the paladin feel about the coup de grace'ing foes you hit with slumber hex? There's nothing against it in the paladin code, and incapacitating and then beheading your foes was performed by the more-lawful-and-honorable-than-you Samurai in real life, so it shouldn't be an issue. But some players and DMs blow up the paladin code to ridiculous, unreasonable proportions.

If slumber-death is ok, consider witch so you have arcane casting and some more healing. If not, go wizard, it's more powerful than witch even with slumber being used, you'd be gimping yourself to not take it.