[quote=chukklehed]
The ability's greatest strength would be it's greatest weakness, since he would have to CHOOSE for the projectile to be affected, and by the time he could shift his focus to it it already hit him.
[/quote]

Bingo. He has to consciously focus on what is and isn't affected, and how much. If you throw to many things at him, he can just say to affect everything, but if you find the right number where he THINKS he can focus on everything, you can get in a enough hits to disorient him.
Look at me, giving out his weakness. :P