Right after finishing the Victoria the Orc quest, my entire map cleared. I had only gone a little ways out the west gate, and when I came down stairs from the library, the blackness over the entire map was gone.

I continued playing thinking I could deal with it, but apparently I am no longer receiving exploration exp for discovering things also. I also entered the well in the middle of the undead lands, and that map is completely uncovered as well, despite me having never been there.

It was also the play session after I had opened the editor once. I only set it up and made a test map. I never opened the main game maps.

This is my only profile, and my first time playing through. I tried loading an earlier save and its map was also cleared. I have not tried starting a new game yet.

If a new game also has a cleared map, try creating a new profile and then starting a new game.

If that doesn't help, try browsing to the '..\Documents\Larian Studios' folder and renaming the 'Divinity Original Sin' subfolder.
This folder contains the saved games, configuration files and a level cache folder. Deleting or renaming it will get the game to recreate it on startup; playing the game from a different Windows user account would effectively do the same thing.
After that, start D:OS, create a new profile, start a new game and check the map. If that is working properly, exit and then copy a couple saves from the renamed folder into the newly created profile's savegames folder. If at least your older saves still have the fog of war, move the rest of the saves over.
If that doesn't help, delete the new My Documents D:OS folder and rename the original back again.

Please email supportdos@larian.com, with a description of the problem and the report.zip file generated by the D:OS support tool (for the PC version). The report will contain system and game information, as well as your saved games. To reduce the file size, you can delete some of the saves in the zip; keep your latest save, as well as the ones before and after when the map first cleared.