I don't really know what Rivek's strengths or weaknesses are, since A) I'm having Coel do my sheet for me (what a swell guy!) and B) we just agreed today to switch to a different class (from psychic to bard) and change all their base stats accordingly. Which makes... three casters, so far. I also figured on being useful to the party by being the driver with the fancy Tesla.
I'm almost certainly going to have the highest charisma value in the party, but I can't really do the talking per se, on account of the character finds the mechanical act of speaking very difficult and always bungles it. I'll do my part to be the face, though. Although, again — literally no face. Astomoi, y'all. Astomoi.