For casters, I been just using the highest ilevel gear I have in each slot be it pvp or pve, and gem for INT in red, Mastery (most my guys are archane mages but it works for affwarlock and discprist also) in yellow and Crit/Sta in blue .... simple and 95percent min max. The extra crit makes up for lack of hit in pve. And not much hit is needed to hit a level 90 for pvp.