I don't think your companions could actually leave in D:OS2, they'd just fuck you over in the endgame if they didn't like you.
Oh! That's even worse! I've never played D:OS2 so this is news to me.
Honestly it's not the only game where something like that happens. NWN2 or DA2 had the same thing if they did not like you. It mostly happens if you do not invest in their personal quest or generally make choices they don't like.
