Today my colleague Johannes Milling wrote an awesome post: Export SharePoint List Data To XML Directly from the GUI He uses the old and forgotten RPC-based web service owssvr.dll (that has existed since SharePoint 2003). This url pattern is used to get the xml-formatted list data for a specific ListView:

http://<site_url>/_vti_bin/owssvr.dll?Cmd=Display&List=<list guid>&View=<view guid>&Query=*&XMLDATA=TRUE

To automate this I have written a PowerShell function. All the details are in the comments: