Problems for Kha'zix
This new pre-season has left of assassin of the void in a but of a tough spot.
Warrior enchantment having its armor pen removed hurts early game so very much. Sure, it gives a bit more AD. But that's not as useful as ignoring a bit of armor.
Tiamat has been dramatically changed. It no longer offeres it's passive to help your clear speeds, putting you behind in farm and ability to gank compared to before.
Last whisper having been changed to only effect bonus armor drastically hurts his ability to successfully assassinate priority targets. When you jump onto an adc, or other high value target, being unable to kill them quickly becomes a liability. Last whisper used to be a major power spike for Kah'zix, and that power no longer is available.
These are the major changes ive noticed from my experience, seeing others play him in the current patch, and what ive seen on the boards.
Im really hopping something can be done for the bug, he's so very fun to play.