I'm going to take your advice and grind until level 60. I just did an hour or so and I'm up to lv51.
The bit where I'm doing the grinding allows you to easily sneak up on about 4 opponents in a row, so I'm just creeping up behind them and combo-ing them, and killing them in more or less one hit.
I found a full walkthrough on Youtube and at the bit I am at, the guy playing is also at level 51 - so theoretically I could beat the game now. I'm going to go up to 60 though just to give me that extra confidence though. And like you say, if that still doesn't work, guess I'll just grind some more!
