Should I use View Submitted Tasks and the Task Persistence tables for auditing and reporting?
No, you should leverage the Reports or Audit functionality.
The task persistence tables are intended to be used for IDM's runtime processing so that each task and its events can maintain the correct state throughout the lifecycle of the task. The data in the TP tables are akin to data in memory while processing occurs, but the physical DB storage rather than in-memory persistence adds an additional level of data integrity preservation.
Because each and every state of each event for every task is logged to TP, the tables can grow rapidly. But once a task is completed there is no need to preserve the TP data--IDM is finished with the data and it should be removed as often as needed to minimize the DB size and improve performance.
The archive tables provide for a backup of the TP tables but they too should be cleared frequently since the data for the completed tasks have no further use.
The TP data is not intended to be saved to provide an historical audit trail or for records compliance. While you can view the task persistence activity in View Submitted Tasks, this is informational only to verify whether there were any recent task processing failures and to assist with troubleshooting.
The intended way to collect historical information about processing activity for both reporting and regulatory requirements is to run Reports via the IDM Reports options or to enable and configure auditing in the individual tasks and via the audit.xml. From the audit tables you can use any tools desired for reporting and compliance.