I don't need to say much aside from you'd think with all those good MUs they would actually do better in tourneys, but honestly I can't say much more than I see a lot more Banes and Hawkgirls in top placements than I do KF and MMH.
Results do not determine tier placement.
Top: Aquaman, Batgirl, Batman, Black Adam, Doomsday, Flash, Green Lantern, Killer Frost, MMH, Raven, Superman, Wonder Woman, Zod
Middle: Ares, Bane, Catwoman, Cyborg, Deathstroke, Green Arrow, Harley Quinn, Hawkgirl, Lex, Lobo, Nightwing, Scorpion, Shazam, Sinestro, Solomon Grundy, Zatanna
Bottom: Joker (Potential Mid)
If I had to break out the tiers a little more, I would list them as the following:
S: MMH, Wonder Woman, Flash
A+: Aquaman, Batgirl, Batman, Black Adam, Doomsday, Killer Frost, Superman, Zod (Possible S)
A: Bane, Hawkgirl, Green Lantern, Raven, Sinestro, Solomon Grundy
A-: Ares, Catwoman, Deathstroke, Harley Quinn, Lex, Lobo, Scorpion, Zatanna
B+: Nighwing, Shazaam, Green Arrow
B: Cyborg, Joker
You can win with a middle character. There are a number of meta-breakers in this game: Bane, Batgirl, Hawkgirl, MMH, and Scorpion. They are going to be winning tournaments because they don't need to play Injustice. They can play whatever the hell they want.