[Rataxes]

It's best to have a thief with decent skills, even if you certainly can get around without one. No necessary or very powerful items can be found behind difficult locks and traps can mostly be easily avoided, though trap setting is a wonderful skill which can be very useful in a number of difficult fights. A bounty hunter certainly holds the most offensive power, his special traps can be thrown (set from a distance) and you can thus use them as a regular ranged weapon (a la exploding potions), only restriction is that the enemy has to be out of the thief's sight. An Assassin does what he sounds like, he turn invisible and move in on a party and get rid of mages or just about anyone in an eye-blink and retreat just as fast while your fighters move in to tackle the now severely weakened party. You could use a Swashbuckler if you're short on melee power, no backstab modifier for him.