Profiles and saves are stored in My Documents. Each save is a folder in the '..\Documents\Larian Studios\Divinity Original Sin\PlayerProfiles\<ProfileName>\Savegames' folder.
Try starting D:OS, change some settings and exit, then restart the game and see if your profile is recognized.
I don't know if folder redirection will cause problems.
Please email email@example.com, with a description of the problem and the report.zip file generated by the D:OS support tool
(for the PC version). Even if NAS isn't supported, the crash dumps included may help Larian figure out where the problem is.