I think the defensive masteries are way better, giving you movespeed and CDR. I also run CDR blues, because then I can get 33% with ionians, far better than what you have. Not sure about CDR quints.
Movespeed is vital because of your short range. You should go in to engage, then reposition while your W is down until you think it's safe to jump in and clean up.
Opening Prospector's is really non-optional in high level games. I often don't sell it, as Jayce's items are pretty costly, I can end a game with ionians prospectors IE BFS/cloak LW and Ex Calling, and that's a game where I get lots of kills and farm.
Remember Hyper Charge is an auto reset. I often go in with W turned on, and miss out on an auto because of this.
Keep farming. You mentioned being able to farm with shock blast. To the skies + lightning field is similarly effective.
Shock Blast goes the same distance whether you place the gate in your own face or at max range. It hits slightly faster with less distance until the gate.
I practically never opt to engage on ranged kiters, because I'm the squishy carry and cannot afford to be baited into cc or a 2v1.
My end build is either (in order of start of construction - I won't finish Ghostblade until the end):
Ionians, LW, Ex Calling, IE, IE, PD (95% crit) or Mercs, Ghostblade, Ex Calling, LW, IE, Trinity Force (70% crit), depending on how many assassins I expect to jump on and cc me.
I go Q>W>E>R, but I can see Q>W>R>E working. Having more Es is nice, as it's a really nice team movespeed boost and it gives you more shock blasts. Talith advocates Q>E>W>R.
Oh, an advantage I didn't mention of the Prospector's, besides making you significantly less squishy, is letting you start with one health and one mana potion. The mana potion is worth over 200 mana, don't underestimate it.