for us the only way so far to do this is by using trusted authentication to make sure you can by-pass Tableau's authenticity_token. We have been using CAS for our SSO, but this can also be accomplished using your own private login page written in java or PHP to get a token from tableau and not by accident open tableau to the rest of the world through your dev server.
After you performed such login there are two requests that need to be done (in the below image within the Loop Controller)
1) Fetch the page and extract the sessionID and the Sheet ID
2) Then do a second request a fetch the actual data.
This will not exactly simulate the load when a user browsers over the tableau pages, but I figured it might be a good indication of it's performance.
Also, make sure you do a load test and not a stress test, I had to add a wait action within my loop to ensure I didn't 'crash' Tableau. Without that wait I could very easily get 500/410 HTTP headers back from tableau and failed results.
You test plan then look's something like this.
Hope it helps, have fun!