First off, I absolutely love The Voidreaver. He replaced Renekton as my favorite champion and Khazzy is a lot of fun to play. His character model is extremely cool and I love his attitude.
My problem with Kha'zix is the holes between his character (what his lore and in game quotes imply about him) and his gameplay. He doesnt eat his enemies, he doesnt devour their bones, eat yordles, etc etc. There isnt a connection and it kinda bothers me. Maybe its a nitpicky thing but I feel like there could be some simple connections made to better illustrate the fact that Khazzy's "Purpose is eating deadly creatures..." This could possibly be done without even changing his gameplay at all.
For example, Taste Their Fear. Doesnt need to be changed technically, but maybe make it so that a killing blow will trigger an animation where he "devours" his target instead of the cross scythe slash animation. Similar to Cho'gath.
I know that the connection currently lies with his theme of "level up by killing so that you can evolve" but thats quite a reach for me.
This would improve his standing as a fully fleshed out character for me.
While we're at it, Kog'Maw also seems to have issues following through on his threats as well. ('Time To Feast!', 'Smell Soft Flesh', 'Keep Coming, not full!')
Just an idea, let me know what you guys think.