with the update's increased q cooldown, the cooldown with max cdr (unevolved or on non-isolated targets) has gone from 0.6 x 3 = 1.8 to 0.6 x 4 = 2.4
HOWEVER, against isolated targets with an evolved q, the cooldown goes from 1.8 seconds on the old version, to (0.6 x 4) x 0.4 = 0.96 seconds. Kha'zix actually has higher isolated dps with the new evolved q than he did previously, making the q evolution VERY useful for dueling, and by extension, splitpushing, killing splitpushers, catching other assassins out, etc.
(bonus AD abbreviated as AD below for convenience)
old evolved q isolated dps: (Base(100 to 400) + 2.6AD)x(1/(3 x 0.6)) =
**(55 to 220) + 1.5AD dps**
new evolved q isolated dps: (Base(100 to 250) + 2.1AD)x(1/(4 x 0.6 x 0.4)) =
**(110 to 260) + ~2.2AD dps**
new unevolved q isolated dps (Base(100 to 250) + 2.1AD)x(1/(4 x 0.6)) =
**(40 to 100) + ~0.88AD dps**
The numbers make it pretty clear that the q evolve more than doubles the reworked kha's q-related dps on isolated targets, so if you plan on dueling a lot the value of the q evolution is undeniable.
In addition, because of the increased non-isolated q damage, and because they replaced the passive's ap ratio with a pretty decent ad ratio, kha'zix gets a big buff to his non-isolated burst damage, potentially allowing him to be much more useful in teamfighting scenarios where the enemy team is positioning well and none of them are isolated.
I daresay the ONLY place that reworked kha'zix loses damage is when he's attempting to burst down an isolated enemy in less than a second. Even following an isolated q with a non-isolated q after a ~1 second cooldown almost always does more damage than a single pre-rework isolated q, not including the additional damage from a single proc of his passive's new AD ratio. Kha'zix's damage isn't going ANYWHERE with the current numbers they're using.
TL;DR
- rework kha'zix's q evolve is really good for dueling
- rework kha'zix has better dps than old kha on isolated targets after evolving q
- rework kha'zix has better burst than old kha on non-isolated targets, regardless of evolutions
- rework kha'zix usually has better burst than old kha on isolated targets if you can accept a damage window of at least ~1 second (with evolved q)
- rework kha'zix loses dps against non-isolated targets, and loses burst against isolated targets if he has less than a second to kill them