I have beaten BP with Nero (After creating festering blisters on my hands that is), although not with Dante. I know it has probably been addressed, but do you still fight "Dante" while playing Dante in BP?
I still recall in DMC3:SE, on all the Vergil boss fights, when playing Vergil, it was "Dante", although it was simply Vergil's character with Dante's sounds and Colored red. Was very interesting.