getXMLContent provide nothing else than a raw export of the document.
I don't use to read OOo documents with Firefox, Mozilla or IE, so I couldn't tell you anything about the readability of the XML.
I suggest you to open your document with the 'readable_XML' option of ooDocument() set to 'on' before using getXMLContent, then to have a look at the exported content with a flat text editor. Maybe you will see what is right or wrong.