I just started act2 during my second playthrough and compared to my first playthrough when everything was new to me and I was excited by the game I see how empty Karlachs quest is.
I had Infernal ore from act1, entered shadowlands, goblin sent me to goblin camp, I played the lute to call drider, kill the drider during the Harpers ambush and went to their camp then talked with Dammon. End of quest. So the quest itself is not even a quest at all, I found the infernal ore somewhere in act1 and had it in inventory. Thats it
. 15 minutes in act2 to complete it and 14minutes of it I did different mandatory things not related to Karlach just to reach the Harpers camp.