every new build has a GOGGalaxy.dll thing in it that's required to launch games

it made calls to gog's website multiple times during startup, and if you removed that part of the install package, it would fail to launch

What I do is block it in my firewall when it asks for permission to access the internet and then the game runs fine. I just HATE that galaxy stuff is included in the offline installers making this step necessary for most games :(

Are you sure you've downloaded the correct offline installer files? Sounds to me you downloaded the GOG Galaxy installer file instead of the offline backup game installer files.

I always click on the 'Download Offline Backup Game Installers' via the website game download page and then download from there. I thought these were the downloads which were not connected to Galaxy, have I been downloading the wrong files?

Nope those files should be fine.