Now I got the info that the Black Hole power Z'rell is using in the big fight at the end is even not from the mod, but is vanilla. Which makes my question moot. Strange, I never lost that fight before (or faced Black Hole), on any difficulty mode, and failed three times in a row with the mod installed (bringing my party wipes in total BG3 from 5 to 8), so I looked for an excuse seemingly.
I managed to win the fight in the meantime without changing the mod or party limits or using cheese (like pre-positioning) while keeping Jaheira alive, so I should have kept my mouth shut and immediately tried harder.
Nevertheless, I don't like Illithid powers ...
