People saying they should take out Catwoman... really?
Batman, Joker and Catwoman are three of the most famous comic book characters ever. Ever. No competition. And all three were in Arkham City. And in Nolan movies. And in MKvsDCU. There was no way they wouldn't include one of them.
Bane makes a big deal of sense because of TDKR. Nightwing is much more than just a Batman sidekick (since, technically, Nightwing isn't). If there's a Batman character who is there just 'cause, it's Harley Quinn... but since she's my favorite character ever screw it all I am not complaining because she's my main for sure.
MvC3 got a lot of complaints because it didn't have several characters the average person wants to see. Seriously who releases the game without a single Spider-Man villain? What are they doing including Sentinel other than pandering to the very hardcore? MvC3 had a fanbase built upon a 10 year old tournament favorite game, not with the average casual. Injustice doesn't have that. Sure, it's made by the guys of Mortal Kombat, but it has no Mortal Kombat characters nor the fatalities or blood that made it so popular on the first place.
They have to go for the easiest route. It's the first of a (hopefully) new series. Have you guys forgotten how the first Marvel Capcom games were mostly X-Men and friends? And now in MvC3 they had the fanbase so they could show more obscure characters. Injustice has to win fans, including casuals. Casuals are much more likely to enjoy the game if they have a large selection of characters they recognize from the get-go, and then they can explore. I mean haven't you guys ever seen that happen? "Hey let's play Tekken *people pick Eddie and Jin* *people starts seeing other characters after a few matches* *they like new characters*"
There's still more characters to be confirmed, even. Haven't Power Girl and Aquaman been all but confirmed? I really can't see them skipping Doomsday either. Who knows who else makes the cut.