Larian Studios Forums Baldur's Gate III Baldur's Gate III - Technical & Gameplay Problems This is one hell of a way to lose the game. (Rank A Bug - Non Prog)

I think it's intended that way. Gale doesn't lose his condition just because he's not part of your team.

Killing him makes it impossible for him to contain his condition.

He does warn you about it (to an extend if I remember correctly).

You could just not have him in your party without killing him.

I'm fine with it, personally. It's one of those "Actions have consequences" that you can avoid by not accepting him in your party (but let him live).