HUGE SANDSTORM PERFORMANCE FIX SPREADING ONLINE. Got this from Reddit.
DELETE EVERYTHING IN THIS FOLDER
on all settings VERY HIGH i'm now getting over 180 frames and NO stuttering. Best framerate and performance i've EVER gotten. Dont worry about your character and stats, those are stored server-side. You can make a copy of the folder just incase you're extra worried. I'm telling you though....the game has NEVER run smoother.