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).
"Actions have consequences" makes sense if you were bound to him in any way. Unfortunately just killing him doesn't mean that he should be able to wipe out an entire team in 3 days.
Currently doing an evil team playthrough with an oath breaker and it's more or less kill on sight, especially if it's a wanderer with no one around and we know that we can take them.
This is going against how we are trying to play and makes 0 sense given the fact that we aren't bound to him in any sense. He would be no different to us than any other npc we would encounter.
And if this magic that he has is so powerful that it could just kill anyone in 3 days, why aren't any of the enemies using it?
The fact that it acts like you're in his party when you kill him is a bug.
