Have you considered using a scheduler to update the data using a script + tabcmd to keep the dashboard up to date on the server?
When you published the workbook, was the checkbox for "Include external files" checked on the Publishing dialog? If so, that is your issue--the TDE file you referenced when you created the workbook was imported into the workbook, and the version on the network share will not be referenced again.
I'm not familiar with Lavastorm...is there some reason that you can't refresh a published Data Source directly from Tableau Server, from Lavastorm, on a schedule? It's always preferred that the data extract live in Tableau Server itself rather than on some network share. If you can't do a refresh directly, you could have a script continually publish the TDE up as a datasource via tabcmd.