I believe the only way to currently do this is by manually creating the hierarchies once the data has been imported in Tableau. However, this sounds like it would be a great suggestion to add to the Ideas section!
Tracy, thank you for the response.
You could certainly manually create these heirarchies from a source retrieval drilled down to the level 0 but considering the number of members in each level, flattening such data would prove to be extremely cumbersome as you could imagine.
Thankfully, I have been able to successfully link Tableau with the source Oracle Essbase cube ... and all heirarchies are preserved!! In developer mode, the speed is not too bothersome (since it is a live connection) so hopefully that will prove the same in published view.
The only issue (which for now I can live with) is that the Dimension members all have generic names. The top level names are preserved but anything below that is "Gen2, Top Level Name," "Gen3, Top Level Name," etc. So it takes a bit of guesswork to get to the appropriate level you want to start with.
Thanks again for the reply. The Tableau journey continues ...