I have committed a new component to SVN to assist with diagnosing MPF (and gstreamer) pipelines: MPF/components/mpf-xml-pipeline-dump.  This component acts as an identity transform, but will dump the structure of the pipeline on the first call to component_process.  The default is a dump to stdout, but the component also supports a "location=filename" parameter to place the XML in a named file.  The dump is performed by the gst_xml_write_file function, and is rather verbose.