Changing every single slot for ilvl 522 items is going to take a while, it always has been and always will be.
So you'll most likely spend you VP on 2/3 items which you mean close to 2 months of farming and maybe there will be 5.3 at that point.
You use them by Raiding, the New rep that includes epics is a Raid rep, so you'll run the new raid and get rep from bosses and possibly trash. I dont expect it to be like the ICC rep, where you can just run trash runs and get revered in no time. Just in case, you dont actually raid, yes you will be able to get it from LFR.