If i sit down there is no bobbing at all from the rear of my Warrior pro. I can also stand up and hammer in the middle chain ring in front without any bob. If i stand up in the little chainring then the back will bob and loose some grip, of course that is fixable if you keep a steady motion, instead of a viscious hammer. The Pivot works great for all around riding.
Of course, the Warrrior pro has a fox vanilla R shock on it with Pro pedal. But i'm sure that you won't have too much trouble even with the X fusion one, as long as you have the right spring rate for your weight.