My only issue with Karlach is that she seems to be wearing, what, ringmail? I just don't know what class she's supposed to be.
Lae’zel, Astarion, and Shadowheart are wearing their unique outfits from the promotional art but Wyll and Gale aren’t. It could be that all of the unique starting outfits for various NPCs, including this one, aren’t done yet.
Looked more like studded leather to me. My money's on bard, though barbarian is a distinct possibility based on her war stories. None of the other classes (that we haven't seen yet) fit at all.
