For Steam, the redistributable files are included in the install folder (..\SteamApps\common\Divinity Original Sin Enhanced Edition\_CommonRedist). GOG may also include them (for D:OS they did with some of the installers, and not others).
To download them, I think it is the 2013 MS VC files that you need.
You can verify files with the GOG version, but I don't think that checks required dependencies, just the game files. In any case, in the (optional) Galaxy client, select Divinity: Original Sin Enhanced Edition in the left column, then click on the More button, and in the Manage menu select 'Verify / Repair'. If you installed the game using the full install, you can still add it to Galaxy.