There's a debate about his competence in one of the books - I think it was Changes. Since the game isn't up to that book yet:
The debate: Is Cristos evil or just incompetence - that is, is he actually dumb enough to believe that the Red Court wanted to make a peace deal and worse, lacks the vision to see that the Red Court would just be regrouping for a final war - one starting 20 - 40 years from now?
As for McCoy being the weakest on the council, I'm not sure. He had refused the offer several times, perhaps because it might conflict with his other duties. Combat wise I'd put his offense strength at near the Merlin's, but the Merlin is better at defense.
Richard