The sated passive is just too strong. On master yi, it reduces his passive to every third hit, procs the cd reduction per aa on his Q, and procs his E. Not only that, it increases the rate of stacking on things like Stattik Shiv and Wit's End, making them even stronger. It also increases fury generation (though tbh, I'm not especially worried about that).
It's a super cool item, but simply too strong on champions like Yi. If it didn't double proc champion passives, then it'd probably be alright, imo.