I would remove the Opportunist talent and add it's mechanic to the single handed and two handed abilities. Because of their small length Dagger should not get an attack of opportunity (AOO).
Even if on your previous turn your rogue moved into dagger range and backstabbed that person? I mean, obviously, an AoO shouldn't trigger if the enemy is outside your weapon's attack range when passing, but I don't see a reason why a dagger user should be forbidden from performing an AoO.
