There's some truth in that, but I'm inclined to side with MIT; when you have projectiles, hitting at all kinds of different levels and with different properties, stuff you can throw at people, air dashes, teleports, lifts/trap moves, a few types of armor, all kinds of different traits, sheild-type moves, and vastly different play styles, etc., there are totally different kinds of considerations than Tekken is dealing with, and that's why I don't think it's a great comparison for balancing a game.
Even if IGAU was 3d, if it had all those things it'd still be totally a different ballgame.
It's really Apples and Oranges in this case -- and like I said, Tekken has had roughly the same ground rules for a while, yet has gone through a couple periods where it was still very unbalanced with regards to specific characters; so if it was just the ground rules that supposedly fix the balance, that wouldn't have happened.
It took Tekken some time to work through those issues, and likewise it will take Injustice some time to work through its own.