I have played through the game two times now. First time with two lone wolf mages, one for fire and lightning and the other for earth, water and witchcraft. The second playthrough was with two lone wolf melee guys, one focusing only on man at arms and the other on scoundrel with two points in marksman to get some utility skills. I played on hard difficulty.
If anything, the scoundrel is the most powerful both in terms of damage and versatility. The backstab damage you do is ridiculous, especially if combined with Bully. You can boost damage even further with oath of desecration and rage for very little investment in cross-skills, but this is not needed in the least.
In terms of versatility, for dexterity based skills, you get two escape skills, two charm skills and three skills to disable (blind, stun and knockdown). On top of this you get invisibility which can both save you in combat, prepare you for combat and steal whatever you want anywhere.
The problem though, with melee is the leech talent. For both my melee guys, there was not one time that they were close to dying. Most of the hits that you get are less than what leech heals you. If you get hit by elemental damage you will soon heal that up again when you later in the turn get attacked by physical damage.