The doppelganger spawned level 40 with an asterisk indicated it is a loot locked NPC (bannable to kill if you did not spawn as I understand it, or doesn't give loot unless you spawned it, or something, IDK). It aggroed immediately but and was chain casting harm touch and boil blood, the chain cast of harm touch seemed a bit excessive so I ran away. The doppelganger leashed and I changed up songs a little bit, but on re-engage he didn't harm touch at all. I was able to just kite/dot him down with bard solo. If he was going to continue harm touching my plan was to keep charming things and throwing them at him while dots did their thing.
Cast alot of darknesses (resisted) and poison nuke (weak) and boil blood which landed because fire dot.