I've had a bit less success this time than I did last time, but as has been said - bonus or no bonus, it's still all down to luck.

I ground three or four things to 10/10 way before the first bonus, then when the first bonus arrived I only managed two or three things - and I ground about forty weapons. This time, I've managed to take one thing from 6/10 to 10/10, and had a lot of almost-guaranteed grinds fail on me.

The odds are better but you can still lose