Turns out i did everything correctly, it was just the web service that wrapped the result in a cdata field. Isn't that kind of strange?
Is there some way i can make the xmlreader parse cdata eventhough it's supposed to be comments?
EDIT: Can i make the XmlReader just parse a string instead of an XMLHttpRequest?
EDIT: Finally got it!
The reader needs to have an xmlDocument that's already partially parsed:
//remove comments from xml-string
//parse the xml into a document
var parser=new DOMParser();
var reader = thisProxy.getReader(),
result = reader.read(xmlDoc);