Hey Chris -
Part of using either flavor of SSAS is you lose the baked-in "goodness" of Tableau's date intelligence - unfortunately, that's just the way it is.
One thing that you mentioned is very interesting - you said: "Using the hierarchies I have created work as any normal dimension would".
I've never seen hierarchies expressed in the Tabular model show up inside Tableau. Are we talking about the same thing? For example, when I publish the sample Tabular AdventureWorks model and connect it it, I see no hierarchies either in Excel or Tableau. Are you? If so, could you tell me what version of the SSAS driver you have installed?
I am using MS SQL Analysis Server 2012 - tabular model. I'm using the drivers that I downloaded from your site.