Ive got 173% Mastery. One FoK Shadow relic and my dps has increased by 75% easily. It works out for me because this just fell into place with the build I already had. So I didnt have to go out of my way for it. I expect a nerf soon and the 915 FoK relic is soon to be replaced by one in Antorus. Maybe I can keep up with the aflocks for a bit.