I could have been me, who already said it. It is my opinion since EA and did not change. I never thought their implementation of cooperation and competition was well done. If A talks to an NPC and plays with B cooperatively, B can still talk to the same NPC and get the same stuff heard as if A never talked to him. Also B never joins into a conversation, like it was possible in DOS1. (Also probably because it would be much harder with up to 4 players.)
Also companions now totally refuse to talk to you, if you not recruited them. I can't remember, that this happened in the first game.
Everything in regards of combat sadly got transformed into binary low bar implementation, which you would expect in a 5 bucks indie game. In the first game putting attributes felt always as it matters, because every attribute hat more than one use. In this game I often did not really cared about them, i never looked forward to this part of the level up. Changing the 'cc resistance' systems and AP-system cut them of a lot of great options in regards of character developement and they failed to find a meaningfull replacement. In DOS1 you also had to max out a skill tree to maximise it usefullness so you had to dedicate yourself, but in DOS2 only Summoner rewards you for doing so, as far as I recall.