Getting parsable deadlock XML from SQL Server error log
Trace flag 1222 will 


  Returns the resources and types of locks that are participating in a deadlock and also the current command affected, in an XML format that does not comply with any XSD schema.


For the limitations (cannot use - Extended events (and that includes the default system health extended event) or WMI event notifications (script that I wrote to log deadlock info to a table)) that is the max you can get.

Remember that system_health session is running by default.