Seriously? This quest was a challenge but it wasn't that difficult. I 1 shotted this but then again, I specced as heals and just sat there healing Khem the entire time while he dpsed her down I was also level 34 when I did this. Theres a reason there are Bonus Series, and other quests. If you speed through your class quests and nothing else you will fall far far behind. Perhaps reevaluate your approach and the actions you take. Get some stims, medpacks, make sure to step out now and then give Khem a heal. Worse comes to worse respec in order to complete it. Not every spec of every class is the most suitable for every encounter, may need to switch things up here and there. Some specs are really only viable on easy mobs or groups/flashpoints/operations while others give more survivability against harder mobs while soloing. If assasin... go respec tank for it see how that goes most likely will be able to complete it. It's not like respeccing is that expensive.
Try thinking outside the box and being flexible, more than likely will be able to complete it once you do.
hes an assasin not a sorcerer. you 1 shot a quest made for ranged dps as a ranged dps.