Tabard doesn’t have any sense if there is no plugin, the roster header is displayed by the plugin.
You can make a dummy plugin which contains the guildHeader function only.
I’ve changed the plugins a bit, please check the latest version of the wow plugin.
The plugin should have have a new function called loadCSS which loads the plugin specific css file.
Also in constructor the provide_sync attribute should set to true if the plugin provide syncing capabilities (this attribute is set to false by default)