Duskblade passive isn't why Jhin and MF are buying it.
I mean, do adcs jump into the backline and drop all of their damage on a squishy target?
Nope. I'd say the majority of the time my duskblade proc is used on a frontliner when I'm Jhin and deals <150 damage.
So, I don't see what making this item melee would do. Or any other item that you claim is better on adcs than the class it was "intended for". You can say for sure that on someone like Jhin, Ghostblade + Duskblade is the optimal build, but "abused" is the wrong word here.