An improved approach to dynamic (user role based) default filter context for Power BI is detailed in Chapter 8 of the Microsoft Power BI Cookbook.
The attached technical document describes an approach for providing users of Power BI, SSAS Tabular, and Power Pivot models with a default filter context. Essentially, DAX metrics are filtered based on characteristics of the user accessing the report and the filter selections applied (‘filter context’). The methodology also supports self-service user filtering following the initial default filter context.
Feel welcome to add comments or questions. My next post will likely focus on the new Tabular Model Scripting Language for SSAS 2016.