Sencha touch with XML
From looking a little into this


You derive mediaContentURL through response.responseXML and title through xml, I would stick in both cases to xml
As you guessed, your approach to getting the mediaContentURL is pretty terrible.
Use getElementsByTagName and attributes, do not hardcode array indexes
Do not use console.log in production code


I would use something like this:

function getItemTitle( xml , itemNumber )
{
  //Skip the title number of the playlist
  return xml.getElementsByTagName('title')[itemNumber+1].textContent
}

function getItemURL( xml , itemNumber )
{
  return xml.getElementsByTagName('content')[itemNumber].attributes.getNamedItem('url').value;
}