I've had exactly the same worries and concerns myself. I REALLY believe Larian NEEDS to have more general testing of the rest of the game before its official release. We've been playing the beta for a couple of months and there's still stuff to fix, so imagine what we could face at release!!
And nothing will hurt a game more than an extremely buggy and unfinished release. A great example of this is Elemental: War of Magic. Stardock had very high aspirations for the game, but it fell flat on its face due to numerous bugs and overall bland gameplay.
Divinity Original Sin has a great platform, and I think has the potential to one of the best in its genre, but it absolutely needs a stable release to attract a solid fanbase. Otherwise I would fear the game will be swept under the rug due to a poor first impression.
