1. Get Level 3 Charged Shot. It's one of Nero's most powerful (and broken) moves.
2. DT's Maximum Bet is a very good move for bosses / Scarecrow massacres.
3. What difficulty setting are you playing at?
4. There is a way to rev instantenously. You just have to hit the Rev button during a specific moment of a move. The ability to do so has to be purchased IIRC.
Dante might be just the thing for you. He has waaay more combat options and his part of the game is harder than Nero's.
I do
DMC3's story was fairly good, I was expecting the same from DMC4...