Sajam
Nightwing In Retirement
Which is fine, and makes NW sound like a great choice but you really have to know NW and these MUs at a high level to do well. So NW could be a great pocket character for these particular MUs but unless you know them better than your opponent it probably won't work out against really strong opponents.One could argue Nightwing's average MU against characters outside of the 4 listed above is about as frustrating as everyone else's MU vs these same 4 characters.
Interesting note: Characters taking names are the 4 listed above.
Besides, other combinations of characters might be more useful than a character paired with NW overall. Having at least 2 characters to cover all your MUs is the most optimal way to play injustice IMO.