If a user has their Outlook setup to store the personal PST files on a network share. This causes severe latency with the DLP Agent.

Network stored .PST files are not recommended by Microsoft (https://support.microsoft.com/en-us/kb/297019) and is not supported by DLP.  If users are doing this and changing to locally stored PST files is not an option then it is highly recommended that add a new monitoring filter to ignore *.pst files with a destination of 'copy to network share'.