I've been playing around with making a speedset lately and in preparation for the changes to Aggramars stride and Sephuz secret I made a mastery stacking set. Unfortunately, instead of it using 75% of mastery (like it does for the other stats) I think it does 75% of 50% of mastery. I would not have made this set if I knew that ahead of time! Heres some pictures as proof:
I was hoping I could get my movement speed up to 162% but I suppose I'll suffer with 150%