The entry I pasted in above came from the stock version of Characters.txt, so I would just delete the entire entry you found above and replace it with the one I posted before. That would reset the Tactician NPCS to defaults.
When I said Main before, I meant it in the context of the .pak files.
So if you go to the D:OS EE folder in your game install in this location:
SteamApps\common\Divinity Original Sin Enhanced Edition\Data
You'll find a bunch of .pak files. One of them is Main.pak which has a lot of the data for D:OS. You can use the extractor tool located in one of the stickies on the forum to extract Main.pak and find all the vanilla versions of the files Scales alters.
As far as the folders go, when you have a Main folder in Data\Mods and Data\Public - files placed in those locations(or Shared folder as needed) will override the vanilla versions in the .pak file. So if you want Scales to stop doing something, you can simply outright delete the file you added from Scales and the vanilla version from the PAK will take over.
But you'd only want to do that in the case of you wanting everything in that file to be gone. So if the Base.Charscript file does all the Master Class stuff, which I think it does, you can outright delete the file. But if there are other parts of scales buried in the modified base.charscript file, you might not want to delete the whole thing and simply replace parts of it.
Which files need deleting or editing I can't say since I'm not familiar with the scope of all the changes.
My suggestion would be to download a file compare program like ExamDiff and use that to compare the extracted vanilla versions of the various files with the ones Scales changed.
