Out of curiosity, what's your complaint about Kha'zix? Because I have no trouble jungling as him effectively and carrying games or working to create great opportunities?
I agree with the Kassadin part of this, I'm really sad with how they've changed him, mainly it just feels like he isn't even an anti-mage anymore, it doesn't even feel like I'm playing anything unique or fun.
They've already stated they are working on Sion (it's currently in internal testing I believe) so that is receiving some progress and they've mentioned Urgot needing attention sometime in the future, pretty sure he was mentioned on the list of champions receiving help this year.
As far as Ahri is concerned, I really don't feel like she is as weak as people make her out to be. She definitely isn't the strongest mid right now, but she is far far away from being the weakest. She can still have a huge impact on the game, farms really well and can participate in seiging and trying to get catches as well as can play the role of a mobile split push in the team composition.