Complaint: Duskblade not functioning as intended

Every Ad champion and their brother is building this item. why? because all they have to do is not kill you by the proc time. meaning all the melee carries? first buy insta win.

Feel like the item should have this stipulation: must do 40% enemy hp in 2 seconds in order to activate. aka, little bit harder than stormraiders surge. not : do damage and not kill them in under 2.5 seconds.