With only standard equipment, the 2 probably go down at 3... Both DD and Elektra could give Batman a pretty good fight. (I think he edges both slightly) Nightwing, however, would be beaten by either, and I think it'd happen much faster than it would for Batman to win his fight. Once Nightwing goes down, the two double team Batman.
Failing that, I actually think Wolverine would do pretty well against them. Just for sheer unkillableness. Batman and Nightwing go down at 3 or 4.
