Except there is a god tier. Kha'Zix is currently there. Can't really think of anyone else from the top of my head, since i haven't watched competitive in ages.
E: Not saying that every champ used in competitive is god tier, just the ones that are really fucking good in both competitive and soloque. So someone like Nunu isn't really that god tier imo, since he requires good team cordination + vision control.