This is very true, they wouldn't stand much of a chance.
Dante's weapons are seriously fun in 3. My fave throughout has always been Rebellion though. But as far as looks, Force Edge is my favourite DMC sword of all time.
Pretty much, Nero was there when Sanctus called Trish 'Gloria', so even though he was incapacitated at the time (iirc), he'd still know roughly what was going on. At least, that's what I think currently without going back over the later cutscenes :]