Sated Devourer and Kennen

Is there any way to improve this?

it takes 4 hits to trigger an effect with sated devourer that should take 5, but vayne can trigger an effect with only 2 hits when it should take 3, thats 50% faster than kennen.

• if at 4 stacks of surge and next attack is phantom hit, that hit should generate the 5th stack AND trigger the damage, instead of just granting the 5th stack without triggering the damage, which it would have done without the phantom hit anyway.

• if at 5 stacks of surge and next attack is phantom hit, it should trigger the surge damage and generate 1 stack towards the next surge, instead of just wasting the phantom hit.