Depends on your style, I like a full party so I usually have 6 characters and 2 RPCs. I take Myles usually through Trynton, after that I go for RFS and dump Myles right before I leave the swamp (he moans then anyways). RFS is my favorite. I also always take Vi, and drag her along everywhere whether she likes it or not
Just to develop her exp wise, and the Hex isn't too bad, she's still valuable, just not as good. To me I don't mind that they take exp, makes the party level slower and have more time to build skills.