Replace Phase Rush as a mastery(with a DFT replacement) and add it to an AP item like Luden's Echo

Luden's Echo is already the most overpriced and second annoying item to build(after rabadon's). Honestly I wouldn't mind seeing the damage proc removed entirely so that phase rush could be added as one of it's passives.

Sorcery needs a sustain damage keystone more than anything else.