Void Spikes is Never Worth the Evolution (Kha'Zix)
Kha'Zix was tuned a few patches ago by taking off the passive addition when evolving his Void Spikes and yielding additional power to his, most noticeably, Evolved Claws. The intent was to give Kha'Zix players more options since pre-patch his only evolution path was: W>E>R=Q. Now however, because Void Spikes gains no additional power, for an assassin champion there is literally zero reason to evolve it now. You literally gain nothing from it since it already slows and the heal remains as is making the only evolution path nowadays: Q>E>R.
My suggestion thus is as follows: In order to make Evolved Spikes actually worthwhile, targets struck now by the Evolved Spikes have the spikes stuck in them, providing vision over five seconds. Additionally, as the spikes slowly fall out, targets struck take 30% bonus damage over five seconds (somewhat akin to the likes of Viktor's Augment Death). This gives the evolution an enhanced, utility aspect and considering Kha's assassin moniker, yields the Evolved Spikes an actual increase in his damage output as should be indicative of a true assassin looking to become stronger.