Man all this Mila hate... lol You people will be sad to know almost everyone is getting those kinds of nerfs, not just characters you hate.
I think it has to do with 5U being F2P. When Tekken went F2P they nerfed a lot of things to make things more easily accessible.
Tekken Revolution is an entirely different fighting engine and different game.
also, that doesn't really justify characters just losing integral parts of their meta-game, unless they are intended to be played differently and based on a whole new game plan. For some characters, this may work if they get new stuff that work well, but other characters just can't do that. I'm not gonna bring Bass or Mila as an example here. It's just that generally, on every system you're going to find characters that will be hit really hard if a major gameplay mechanic is changed or removed.
Let's be logical here, if the only character that is meant to have frame advantage from a chain OH break is meant to be Bayman, then why would anyone play him when you have a character that has faster mix-ups and gets more advantage after the same chain OH breaks and even has built-in mix-up after the break? That just makes Bayman the 'Oh yeah, the guy with all those OHs'. But make him unique and you'll have more people gravitating towards him.