Hi. I finally was able to obtain all the wad files utilized by DE, by either steam, patching or looking into the internet. Although, there is one particular wad file supported by DE/DE2 which is Hexen 4-map beta demo. For the sake of completism, I dug everywhere looking for this rare wad and the only reference that I found on the file is the Doomwiki about its size and hash.
Beta 10,615,976 9178a32a496ff5befebfe6c47dac106c
Since it is not a commercial wad, I think it is fair to ask for such wad file here, since DE/DE2, to my knowledge, is the only engine that asks for such file.
Thanks a ton!