User blog comment:Hyxaru/Typhoon Claws rework/@comment-24862418-20180412052727

Guinsoo's Rageblade is good for Mixed Damage Champion (builds both AD and AP) or with on-hit effect like Varus, Kog'Maw, Irelia, Jax, or attack a lot... With your design, there are some big different and maybe problematic.

1. Champs with 3+-hit effect like Vayne's W, Jhin's Passive are very unpredictable. Imagine like this, Vayne attacks 3 minions to get Phantom Hit then Q, 1 2 3, she proc W on you. So, this item is at best poking in laning phase.

2. There is no time requirement between each hit, so I assume the time between the third and the trigger attack is unlimited. I think you should make it like Yi or Jhin, not attacking will reset the passive.

3. Other than damage, some attack effect also grants addition effect like Xayah passive (one atk, E, root), move speed (Gnar), armor penetration (Vi).

As you can see, on-hit effect is more controllable. 3 attacks can do various things that we cannot expect, and may nerf a lot of champs. A mechanic like Phantom Hit would bring a lot of problems, then why should Riot add such a problematic item.