I don't know what your problem is with Act 3. It might not be as good as the rest, but it's still plenty good and better than most modern games. I just killed >!Gortash!< after completing nearly every side quest I could find and I haven't really had any issues. Sure, there's a few things that could be a little more fleshed out or that feel like cut content, but not much. I also don't know how many of those things are actually cut content and not just references. Like in Cazador's manor there's >!a body with a note talking about a sleep potion and acid poison. I'm pretty sure it's just a Romeo and Julie reference. He took the sleep potion to fake death, his lover found him apparently dead and killed herself. He found her dead and killed himself.!< There may have been plans for a quest there, but idk.