Well, I can see why devs wanted to make 4 companions as protagonists - that way in case other players join in and turn it into MP session they all can initiate conversations. It's why DOS1 had 2 protagonists - it was a 2-player coop. And since devs made DOS2 a 4-player coop I don't think 4x samey conversations with npcs are gonna go away.
On the other hand, nobody forces you to talk to npcs with all 4 companions. I certainly didn't, unless some npcs weren't willing to talk or aggroed on some companions. If it were a true SP rpg then the dialogue system would have had companions interjections and only the protagonist as the conversation initiator, but since it isn't I too doubt that anything will be changed just for SP.
