Played a few hours last night, about 98% of my matches was with Atrocitus and the other 2% was Batman. Didn't play as anyone else.
I LOVE Atrocitus, he's very fun. I just love his safe pressure, constantly harassing the opponent and chipping away their health. Once you have them scared of you, throw them for a mix-up and try to open them up. His restand (Back + 2, 3) -- along with Dex-Starr (which can give you a hit of armor, allow you to shoot a fireball at pretty much anytime for even safer pressure, and even new/extended combos) -- really completes him.
Overall the game feels more smooth and less janky and floaty like the first game. The camera is a lot closer to the characters, it's not quite as far back as the first game. The outros aren't skippable, but that's okay because they are SUPER short -- which is good. I'm talking about just a few seconds and you are already rematching. Speaking of which, the load times feel about the same as Mortal Kombat X, so they are fairly quick and you spend very little time watching the game load. Lastly, the graphics is easily the best out of all the NRS games by far.
Overall, it feels like the took Injustice 1 and put it into Injustice 2. Then fixed and improved everything and added tons of new stuff on top of that.