The online itself is really good, actually feels like an improvement a little bit from MKX. I'm from EU and played 200ms matches and it seems like it didn't rollback as much.
Only lag really is in the character select screen, anyway the thing that i hope gets addressed is nerfing Superman, Supergirl and some of Batman's stuff: Batman's ji2 is way too good, you can anti air it but it's really fuckin tricky and inconsistent. And also his ex batarangs being +34, that's way too plus imo. Would be cool if they reduced that some. And when it comes to superman, nerf his damage, 1 bar 65% is way too much damage for a character. And make f2 like 10 or 11f.
EDIT: Like Compbros mentioned, Canary sure needs a d2 buff. And fix the b133 string, it's so horrible it's not even funny. The string has 3 gaps, the first hit is a high and the start up frames is like 15, 16 or something like that. Doesn't even end there, it's also unsafe on block, i don't think i have seen such a bad string before.