This is not a sandbox RPG?
Oh yes it is. In fact, it is so sandbox it almost feels like a kind of single-player UO.
Old storybased games like Baldur's Gate, IceWind Dale Planescape Torment... hell even Knights of the Old Republic or Dragon Age: Origins say the game is done when it's done.
None of those give you the freedom to do all sorts of crazy stuff that D:OS gives.
I know action-RPG's, sandboxes and stuff are common now
ARPGs are very common now indeed. But sandboxes.... Nowadays only minecraft comes to mind, and it's not even an RPG (is it even a game? more like a toolset?).
people might expect that the MQ is just a part of the bigger picture like in The Elder Scrolls, but it's really not the case here.
I would never compare TES to D:OS. I mean, if TES are really supposed to be sandbox RPGs, they are very bad ones. In fact, I have always played those games as first-person ARPGs. The ways you can interact with the world are just way too limited to justify calling them sandboxes.
Edit: Wow, this made me think.... A Divinity Online based on D:OS's engine, direction and features would be f***ng awesome. It could be to D:OS as UO was to UVIII. Tears of joy. That might be overly wishful, but hey, maybe a mod...?