The debate in this thread seems to be reality versus idealism. Ideally, a Cleric should just be there to make things easier, and content should be totally doable without one. In reality, ain't gonna happen. It just won't. Players won't stand for it, and devs won't make them.
I would put cash money on the upgraded Combat Superiority not debuffing properly, but I can't prove it as I don't know how it was intended to work. What I do know is it seems to be up a lot more often at 4/5 as opposed to 5/5.