The steps you describe at the beginning should work.
Connect to Oracle
Import All Data
Data > <data source> > Publish to Server
Connect to Data
choose the data source you published (do NOT click the down arrow button that appears on hover)
The data source should show up with the square Tableau icon that indicates it's going through the server.
You can't just publish the TDE by opening it directly, because then it does not include the information that it came from Oracle.