User blog comment:Ozuar/Kha'Zix - My Conundrum/@comment-4290320-20130410180504/@comment-6435632-20130410190046

The increased damage from the isolation bonus on an evolved Q is actually extremely powerful if used in the right situation. It's included on top of his normal damage, and deals 12% of the target's missing health. This is large damage against anyone below 50%, but even before then it's gradually more and more damage as they lose health. Beginning a combo with Taste Their Fear and ending it with it is basically a kill against nearly anyone. Evolving his Q is also the only circumstance where Kha'Zix is nearly equally as effective in killing tanks as it is in killing squishy targets.

It also allows him to easily solo Dragon without help, as well as murder people even easier while roaming or chasing. Its increase to attack range also helps while chasing.