Link Shell Extension works great. Just follow the instructions, very simple to do, all you got to do is highlight the folders you want to do, for example Data and Interface folder highlight both and right click and pick as Link Source then go to the wow copies dont open them just highlight the copy and right click it and do a drop as Symbolic Link and done. To check the folder to make sure that it did as you asked just double click and open it your folder that is Sym Linked will be in there both the ones you highlighted and picked. Updating your main folder during patches is cake, open your main folder do the updates then go to your clone folders and delete your Symlink folders and re sym link them and copy your main folder wow execute into your clone folders.