I got to Khasava yesterday, thanks to some MQ advice from False.
My feedback, I'd extend the crystal clicks by 2-3 seconds. I'm getting to the 4th or 5th crystal and Khasava has summoned the punishment. Obviously it should be tight, but there's no margin at all for error.
Banishing out of the zone to Hidden Forest....please no. It's near impossible to run them back in through 2 zones and down to the encounter, and keep clicking the crystals. Maybe banish to the hall & stun Instead?
Khasava, Adds and crystal clicks at same time...could we offset this, so maybe if adds spawn they're timed, so if the don't die the heal or power Khas up? Then as soon as they're dead/soul consumed, move on to crystal clicks.
Lastly - not sure if this is a bug, but I'd done a few bosses the previous day. Valik respawned, Khasava despawned. I then had to kill Valik, Maestro and Vasella again. Once i did Khasava immediately respawned agro and went into chanting and powering up.