9 months ago - Heightmare - Direct link
You're absolutely not downloading 56GB of data every update. The downloads themselves are quite small, but due to how the games data is packaged and how Steam likes to handle storing and updating this data it can result in a lot of files being moved around on disk. On slower hard drives this can take a while - it's likely if you have a look in the download page in Steam you'll see it goes from 'Updating' to 'Patching' then to 'Installing'. Only this first phase is the actual download.

Things can be adjusted at our end, but any improvement to install time will be to the detriment of either download size, game load time or several other factors.