If you cloned him you’ve just doubled the problem since a cloned tuvix is still Neelix and Tuvok. Even if you split one copy the other is still made of people who deserve to live their own lives.
My trick for Balthazar is to fight him in his original room. Don't fight him in the nightsong's room.
If you fight him in his original room you just have to deal with 3 ghouls that are a joke and his big bruiser plus Balthazar himself. Balth is easy to down in a round or two depending on your party comp and then you can just clean up the remaining undead. Once I discovered this strat I've never fought him in the nightsong's room since.
How i feel when my party enters the Shadowlands in BG3 and Shadowheart is like “Shar loves me, the curse doesnt affect me!”
Bitch you're wearing a glowing mace of lathander. Why would the curse affect you?