Killed the boss on third attempt after I stopped being so f***ing supid. Khem was dead but I still had 80% life left. You have to do 2 things: 1. Pet Control Send Khem Val to her and let him tank. When she casts a blue ring on the ground set Khem to passive and let him run to your side. She will not move and begin to channel a lightning AE. After the AE subsides let Khem attack again. Khem will eat her single target force lightning for you. You can also use Khems spell "Bear Pain" to reduce damage to Khem by 25% for 12 seconds. I didn't use it myself (in fact I didn't even know it existed). 2. Range DPS Do absolutely not forget to cast your Mark of Power. Alwas stay at max range. Use dots and all range DPS you have. Means: Recklessness, Crushing Darkness, Discharge (with Lightning Charge), Force Lightning, Death Field, whatever you've got. You can also try to interrupt her heal with Jolt and Electrocute, but this isn't even mandatory. As a sorcerer: No problem at all. Pet still lives, full health. As an Assassin: As soon as your pet dies, use deflection and continue to apply range damage. Flee the AE effect. If all else fails you can always buy a big willpower stim and a large health-pot to restore 50% of your health. But I think it's actually quite easy if you're doing it right.