1) I could do it in a lot of playthrough with Druid, Sorcerer, Bard and Barbarian. Most with Lae'zel, Shadowheart and Whyll in the group. But I have activated the "Weighted Dice" feature.
2) The last time I did it in the way is serval patches ago. There Ethel duplicates herselft two times.
Maybe you can select the option to knock out the enimies.
I've found no game mechanics difference between knockout and killing, the person disappear in both cases.
Now for most that doesn't matter, but one of the "mask" people is a future quest NPC in Baldur's Gate and the other person that is an issue is Helsings apprentice, she is still gone if you knock her out. Only the human vs Zevlor scripted knockout seems to have recovery.
