The best we can suggest is that you customzie the report to remove the XML. The cool thing about our use of RDL is that you can edit the RDL and call functions. For the specific field value in question, you can try to replace the current value =Fields!TEST_C.Value to something like this:

=Replace(Replace(Replace(Replace(Fields!TEST_C.Value, "<?xml version=""1.0"" encoding=""UTF-8""?>", ""), "</Value><Value>", ", "), "<Values><Value>", ""), "</Value></Values>", "")