I've encountered almost no bugs on my playthrough with all available patches guys (and this is the version that's on GOG). I'm talking about all of the official campaigns. I have a feeling that you exaggerate a little. Or was I so lucky?
I play GOG version too. I describe BUG as something the coders were not able to foresee that the players would do. So, if you played the game logically, you shouldn't have much issue. The problem happens when you go out of the way and try something crazy.
However, since NWN2 has a serious amount of bugs like the load problem where extra spells are lost, I believe you just did not care about those small issues or did not notice them at all. For example this one I wrote on my review.
15. I learned that The LOAD function is generally bugged because of the system how it works. Because of this, extra spells you gain from gloves, rings or amulets won't work the first time you load. You need to rest and replenish them. I am experiencing this for Qara, Sand and Elanee. Also, Grobnar's inspirations wont work first time you load even if they seem like working. You need to select an other inspiration and switch back to make it work again.
Still, as alcaray said, I loved NWN2 and it is a great game, made with love despite its terrible design and coding.