I found a “golden nugget” for using Analysis Services Cubes (SSAS) with Tableau.  There is a Knowledgebase article on the topic that is a little dated BUT the attached workbook with the common design pattern examples is really excellent.  There do seem to be a lot of customers using Analysis Services Cubes OR trying to figure out how to do it. Keep this handy.

KB Article: http://kb.tableausoftware.com/articles/knowledgebase/functional-differences-olap-relational

Design Patterns: http://kbcdn.tableausoftware.com/workbooks/adventureworks_cube_on_scdemo-dbs.twbx