I was happy because it kinda irked me how no matter how evil i wanted to be my companions never left me. I mean, Fenris respecting you as a rival becuase you're pro mage is reasonable, I doubt even in DAO he'd up and leave you for that, he'd just be disappointed but I mean, Night Terrors. You literally, can side with the demon and sell Feynriel out. That is so much fucked up that I'm surprised that nobody reacts too negatively about it, it's literally forgive and forget. It's decisions like that that should have a consequence that involves a companion wanting to leave and not be associated.
And for the record, even if the world is ending, who's to say that the person who left can't gather their own alliance, blah blah find their own solution. Just because you're the last hope doesn't mean you're gonna succeed. Personally if the "last hope" was a total douche I'd leave him, I'd rather die than work with a person I just couldn't work with, which is what DAI is doing I assume. LIke everyone said, i doubt they'd leave over small things, you'd have to personally try to kick them out and antagonize them to ****** them off for them to leave. I assume is how it's gonna work. Which would make sense.