I think the approach is wrong.
To me Talon should be changed into an assassin that wants to stay in the fight a little more.
Easiest fix for his is his passive.
Passive - Shadow Step
When Talon kills an enemy champion he becomes invisible for 0.5 seconds. The next basic attack he deals to an enemy champion applies his current rank of Cutthroat to the target.
I don't think anyone would disagree that his current passive is very lacking. The change to his E was completely needed. Which everyone also seems to agree on.
This changes gives him an escape and gives him the option to stay in the fight a little easier. If this is not enough it can added that his Rake's CD is cut in half on champion kills as well. But we don't need another Kha'Zix. And if anything this would make him need a nerf of a sort more than another buff. But overall I think it would put him in a good spot.
And I do agree that there's no reason for him to not get the ability to interrupt abilities on his E.