Look to make sure your TDP's are actually deleting their backups.  I
was burned by DB2, Oracle and MS-EXCHANGE platforms not sending the command
to TSM to delete their old backups.   These files are NOT really being
managed by the copygroup policy the way you may think they are.  The client
must tell the server that the file (the TDP backups are all date/time
stamped and therefore UNIQUE) has been deleted.  Then your deleted file
policy in the copygroup is in effect.
Matt