I have Questing skill 2 lvl. And Quest kill Archimage 5 times that is impossible on my lvl after i die few times for dust. Its need to auto reset on some lvls or reset button to do it once in day or 3 days.
Another thing i dont know bug it or not. But i found few times empty Bone Piles. Never seen it before.
Another suggestion. Remove or make something with quest kill 5 chaos. I spend 1 hour to find a single one chaos on surface and found nothing. Ok then i go UW and try to kill chaos from dark chests. But they teleport! Do this quest extremly difficult not because it hard to kill chaos npc. But because it pain in ass to find a single one.
If you do not want delete this quest, then make them stay some time in UG after opening dark chest to fight them.