I guess for Gluster logically only wp-content will be needed to replicated.
As basically we do not
make WordPress with the OS itself but simply run it from publicly accessible folder (unlike a web software like a Git which needs pure CLI work), practically on MySQL database, its the master server's configuration which will direct which directory has to pickup from which server.
I think, there are quite well knowledgeable peoples in Server Fault (http://serverfault.com/), they can share their own experience with you. I replied on theoretical assumption which actually you might have thought, but theory might not work !