To ensure a mod is completely gone, go to the following locations (on Windows 7) and delete them...

For .pak file mods:

1) C:\Users\<USERNAME>\Documents\Larian Studios\Divinity Original Sin\Mods

For any mod that you fiddled with yourself (delete folder <MODNAME>)

2) C:\...\Divinity\steamapps\common\Divinity - Original Sin\Data\Mods\<MODNAME>

and (delete folder <MODNAME>)

3) C:\...\Divinity\steamapps\common\Divinity - Original Sin\Data\Public\<MODNAME>

Obviously directory locations may be different on your machine, but you hopefully get the idea.

If you actually fiddle the game's Main data files...well then it gets tricky. Hopefully you haven't messed with anything in the \Data\Public\Main\Assets\Sound folder, because if you HAVEN'T just delete everything else under \Data\Public\Main EXCEPT that Assets\Sound folder and you should be back to default. You may also need to delete anything under Data\Mods\Main as well, but I'm not sure on that one.

Somebody correct me if I'm wrong, please.

Take care!

p.s. and omg, I agree with you wholeheartedly; this game is so awesome and such a late find for me (like a month ago), but I can't understand why there isn't this HUGE modding community flourishing around it yet; it's been what, about 8 months almost? if I had to guess I'd put the blame on lack of sufficient documentation from Larian?