Ah, but it was an absolutely perfect move for DRAMA.
A team member going rogue to do what they truly believe is right, and they maybe aren't even all that wrong? That's the kind of constructive conflict I dream of encountering as a player.
I'm firmly in the camp of "Durkon made the right decision." We've already seen Roy tell Julia that he'll kill Redcloak if he has to -- he's a good team leader, but he's not seeing the big (cosmic) picture.
That seed of doubt is going to fester in Redcloak's head, and crop up soon enough. When they have him at their mercy, hopefully he'll remember that negotiation was their opening play.
(NS: I continue to be baffled by predictions that Minrah's going to get Stuffed in the Fridge. It would be such a weird, dissonant story beat.)