Backward thinking riot OP
"At the moment, the monster damage in W ties Kha'Zix to the jungle. We'd like to give him a chance to spread his wings elsewhere, so we're swapping that power for a bigger Q buff than the Duskblade changes warrant alone."
Kha'zix is a jungler. He does his best work, IN THE JUNGLE.
Next thing you know its "Hmm, adc's ability scaling off ad ties them too much to bot lane, so we are gonna make all their abilities scale off magic instead" or "Hmm tanks are too tanky, lets make them utility supports that are squishy so they are not tied down to their role"
Now that my rant is done, a stronger Q is pretty good but that W damage was to help clear a little better in the grouped camps. Seems like riot just likes nerfing khazix in some form or other. granted his Q will be destroying people but he already did that. why not make W worth something? no one ever evolves W, let that sink in (except when they win the quest to get that final evolution)