We can simplify every game and find tons of common things that differs just a bit. But that is! This is the case of everything - that difference. The more complicated and different some aspect, the more it -- sorry for teh tautology -- differs. DAO's plot/stroy is different. There is a lot of tiny differences on the DAO's picture with uses teh same canvas (genre) as Divinity 2 does. But those differences is what makes DAO special, different from Divinity2 and better in some cases. Can you die in Divinity 2, saving the world? No. Can you save it with group of your friends, having an army behind your back, that trust you and put their lives in your hands? No.
And you telling me that level of realism of those two game equal, lol. Sometimes, the blind fanboism is like a fog - you can't see anything.
Ahhh... the delights of utter irony.