When compiling, the path to the referenced dll is valid and will work.
However, when running the application, the referenced dll must be accessible by VA. Since the plugin/inline function is called by reflection, it can remain in a subfolder, but referenced assemblies must be, 'visible' to VA. That means the dll must be in the same folder as VA, or in the GAC (if that's even possible, as VA is signed... can't remember all the rules). That's just the way it works and, unfortunately, there's nothing that can be done about it. If the documentation is misleading or wrong, it needs to be changed. Sorry about that!