Hey.
So i had same problem, ACT I was running fine. But after getting into ACT II, game start to shutter. Loading take a hell of a time, and overall spikes nearly torn my nerves. I Tried to start a ACT I and it was running fine again... EA works fine before too. And i get idea to check a game folder... and yeap, there was some files from EA (Atleast date that they were changed or created was old). I tried to delete them, and then repair a game through a steam (I tried to repair it before too, but it dont help). So, i'm 30 mins in act II and it seems fine :) So maybe complete uninstall (Check steam game folder for any leftover data just in case) could help :)