My proposed 'bugfix" for Kha
Evolved Passive: Unseen Threat applies a 75% decaying slow, or a 1 second root followed by the usual slow. Evolved Q: Deals %missingHP again. Evolved W: Stays the same. Evolved E: Stays the same. Evolved R: Exiting stealth releases a shockwave that knocks away all nearby minions and gives Kha a 2-second shield based on the number of minions struck (so it's Xin's ult for minions). Still gets 3 charges and the increased duration.
The point of R is to get isolation on a target when they're in the middle of a creepwave, and since it doesn't help waveclear there's no incentive to use it for anything else (maybe popping it for the shield if a Cait is ulting you, but that's rare and fun). The point of evolved passive is to keep your target trapped in the no minion zone you've created.
Now that we can have 3/5 evolutions, there are more combinations: Q/E/R: the leapfrog R/P/Q: kill the split pusher P/W/Q: you're 0/15 and just want to peel Q/P/E: the jungle assassin
One alternative to evolved ult is to have it pull the minions in, so that you can decimate the whole wave with a cast of
, but that makes it tempting to use his ult to waveclear.

;)
tanky-bruiser Kha'Zix to come back with such a change, where he jumps into your back line, takes out your Squishy, and then takes a wombo-combo initiation like a tank.