I believe this is related to oracle drivers not being installed on your local machine. 8.2 desktop requires drivers to be installed on the tableau desktop machine. Try to install the drivers and see if you can create an extract.
You can find the drivers here, Drivers & Activation | Tableau Software
If this doesn't solve your issue, were you able to generate any extract on 8.2? I'm using 8.2 desktop and being testing the beta as well. I haven't found any issue related to extracts.
I have a similar problem. Anything beyond server 8.1 already has Oracle drivers installed. I've tried installing drivers for 8.2 from download site but still get error