I agree with some people here that the couch co-op for this game wasn't worked on enough to be ready for release.
The dynamic split-screen is the biggest indication of this of course. But also: - Reading books (not notes) in split screen is a pain. We get an open book that doesn't take advantage of the horizontal space and we are left with super tiny text. - When both players are handling inventory at the same time and one decides to apply a Filter or Sort, something happens that affects whatever the other player is doing at the same time (i.e. They were trying to select an armor and suddenly the pop-up window closes) - There's not a proper way to handle cut scenes. They seem to be handled completely separately for each player, and me and my partner have missed parts of them because they initially only show in one player's side of the screen.
Anyway, going back to the dynamic split-screen... For me that's the biggest problem! Especially in combat!! I must say that I don't really like the decision of allowing players to do things simultaneously. I think it goes against the idea of TURN-BASED combat.
I hope that this design choice isn't the reason why we are getting the forced split-screen. Because if it is, I think it was the wrong call. It's a step away from turn-based combat, and people who fell in love with turn-based games (especially the D:OS series) are the ones getting hit the hardest.
I remain hopeful that all of this will be addressed eventually, but Larian not saying anything about this makes me worry a bit. My partner and I had been waiting for this game for years, expecting at least the same level of co=op experience as in D:OS, but so far this experience has been worse.
I heard ppl say that two people bring able to do things simultaneously is precisely the reason why we have this perma-split screen situation. Personally I couldn't care less about simultaneous actions. Give us the big screen couch co-op experience!