I htink the top 5 model doesn't work for Injustice. I would accept a top 10 or maybe top 8, but after this winter tourney season I think its clear a concise top 5 doesn't exist.
mmh, superman, zod, ww, ba, zod, aqua, batman, batgirl easily "top 5" material barring their absolute worst matchups / execution / stage barriers (Which some of them don't have)
Then you have like bane, sin, flash, and lantern who would probably be top 5 if not for someone in that first list who ruins their life.
Everyone else has to have a secondary.