A good test as to whether the cost of something is acceptable or not is to inflict it upon the protagonists and everything around them. If they wouldn't stand for it, then there's no reason for anybody else to do so either. We already know that if someone came to the Scions and said that the people of Limsa Lominsa needed to die in order to stop a greater threat then they would stop at nothing to find a third way forward and fiercely oppose such a plan.

Of course, quite often the very same people who defend Venat and like the Scions mysteriously are firmly against the idea of any meaningful harm befalling their favourite characters. Funny, that. They're perfectly happy to demand that everything else is inflicted with disproportionate suffering and trauma, though - especially if it's a character or faction that they detest!