The only Batman character who got straight up cut from I1 is Batgirl - Nightwing's moveset is gone but the character of Damian Wayne is preserved as Robin - and we're getting more of them. That game had 6 Batman characters in the base roster (Batman, Nightwing, Joker, Harley, Bane and Catwoman), which was 25% of the roster of 24 characters. The percentage was reduced post DLC where we only got 1 additional Batman character out of 6 DLCs, with a total of 7 out of 30 post DLC.
If the leak is true, however, Injustice 2 bumps up the Batwank. Out of 28 characters, the 6 from the original come back, plus Poison Ivy, Scarecrow and Mr. Freeze, so we're going from a fourth to a third (9 out of 28) of the roster being Batman characters.
I remember a common complaint lobbed at Injustice 1 was that there was too many Batman characters compared to other DC properties. Yet here we are.