You can reroll 1 stat / item, you can reroll it as many times as you want to, but only that one stat. So for an item to have a chance to be perfect with the help of the Mystic, 5 out of the 6 rolls still need to be perfect. The last one you can fix with the Mystic, as long as you can afford the rerolls.Quote from snowhammer
Correct me if I'm wrong, but with loot 2.0 there is no "hunt for perfectly rolled legendaries" step. You use the Mystic to do that no?
Edit 2: Got some bug, it's alright now,