Act 3 is bad, I'll give you that but to say it's in alpha state is exaggerated. However, Act 3 should be reworked in large parts for the definitive edition.
While I appreciate that this will happen, this is a bad habit we are allowing Larian to get into. They did this with DOS/DOS2 where the early game at launch was outstanding and the later game trash until they eventually fixed it. I think it is no obvious why this happens with them focusing so much on the EA and then not putting the same level of effort into the late game. Right now, with this track record, it is very unlikely I would ever again suggesting buying a game they develop until a "definitive" edition is released. This approach hurts them for early sales, they need to find a way to stop this behavior.