Is it possible to create a dual graph with stacked bars? When I try, tableau gives me two separate dual graphs, one for each bar: http://public.tableausoftware.com/views/HealthCosts/benefits?:embed=y
You need to configure the Marks panel separately for line (Coverage) and bars (Contribution). Download the embedded modified workbook to see how the Marks panel is configured.
Essentially, you need to use < and > arrows to get to the line or bars, and put 'Worker or Employer' on colour shelf for bars, and nothing for line.