General nerf to AD assassins
They're all in a too good spot right now. The only one who still struggles is Kha'zix, so I have a simple proposition.
Remove armor penetration from Malmortius.
Put it on some other item. One that does not grant such a huge spike in survivability early on when against AP midlaners.
Make Malmortius a more bruiser oriented item like it was last season, with more survivability and less damage.
Btw, I am a Shaco player and often make Malmortius (last season I wouldn't). This is not a biased mage-main thread.