I think this is a good build. I haven't tried it yet, but I think you're too much crit dependent for your low crit chance. Your only crit item is Infinity Edge, but all your runes are crit dmg runes. I think Armor Penetration would be better for the Marks and Quints (Greater Mark/Quintessence of Desolation). Everythink else is nice, you have very much damage and for your more or less low attack speed you have Rapid Fire. +1 from me.

Your masteries are dumb. You put 4 points into Sorcery and 22 points into Offensive tree but you don't take the best skill in the tree? Get 1 point of spell pen. It's worth 400x as much as an extra 1% attackspeed.

some desc about playstyle would be welcome in this guide. I see potential here :P