actual we do not use CV for backup of our fileservers, but it is planed in near future.
With our actual backup software, we are also faced with the this problem. If PST files are attached to Outlook, every day a timestamp is written to the PST and so the backup tool selects this file for backup.
To avoid the backup of lots of PST files we are planning to use block level backup with deduplication. This should only backup the changed blocks and not the whole PST.
But at the moment we have lots of trouble with this mechanism. Backup works ok, but the restore do not.