For some reason most people play Conqueror even tho they never reach 10 stacks in the whole game, much less they do before it's of any use in a fight. In lane you opponent is already dead by the time you stack it. That's probably one of the reasons his winrate skydived.
I think Domination and Dark Harvest are probably the best choice for primary. We can open an argument for secondary. Your choice makes a lot of sense but I would probably go Sorcery for Mana and CDR (since realisticly you can only fit 20% into the build). One other option would be Inspiration for magic boots and Future's market in order to facilitate reaching the itemspikes so important on Ezreal.