Yes, that quest is pretty tough, but not impossible thou. Are you playing Elementalist or Summoner?Now I am LV 16 but that boss of could Trail quest ( Hidalix maybe ... I do not Remember the name in this Moment ) Is still too strong .
For now I am trying to stock hi - ho potions , cold resistance potions / equips and other things for being able to get a Better grip .
Anyway, in either case, if you dont have an Ice Golem summon, just buy a few scrolls of it and equip Griss with all Ice resistance you can (instead of equipping those yourself). The Ice Golems will make your life a lot easier; and use weapons with fire element.
Im not going to say that it will be easy, but it's doable. Clear the dungeon all the way up to the dragon, and then lure it to follow you around, as to have it fighting your team alone and away from the tons of minions that will keep spawning from the portal. Once you kill the damn dragon, no more minions will spawn. It's not that hard actually. If Griss get to sleep, have the dragon follow you all the way up to the exit of the fortress, exit and she will be fully awake once again, heal up, summon your ice golem (from scroll or skill) and get back into the fortress so that it will be wait for you at the entrance alone. Now things should be a lot easier. If absolutely necessary, have 3 or 4 scrolls to wake Griss up, but try to spoon feed her with health potions as often as possible to avoid having her fall asleep and bam, it's done.