I'm going to be a dissenting voice here. I LIKE the idea of creating a single character and having other, fixed companions with their own points of view and reactions. I am not interested in role-playing versus myself - I wasn't in D:OS 1, so much so that I didn't play D:OS 1 on release - I waited until the AI personalities were added before playing for the first time.
I do not mind that I won't have the opportunity to customize my entire party, and that they will have their own distinct roles and strengths. It just means that I can focus on tailoring MY character in a specific way.
However, I'm a bit less certain on the AI companions never leave or attack. That really depends a lot on the specifics, though, and I have no idea what those are yet. It could be good, it could be bad. I don't want to be forced to take a spy for the Divine Magisters with us in our party, but other than that, it probably doesn't matter so much.