I am still going to say Gambit is the deciding factor here. The old Psylocke only had telepathy which is useless against Gambit. Gambit can win from a range and would be able to least keep up with Psylocke in hand to hand (or sword to staff) combat long enough to blow her up.
Gambit/Nightwing win this still(because of Gambit).
Cassy would probably rape Nightwing though.
Now, if Gambit wasn't allowed to throw anything or charge clothes, weapons, etc, this fight would be even. What about Psylocke/Nightwing vs Batgirl/Elektra?