What are your dimensions? Please can you post the sample app? And what do you have in vDashboardMaxDate? I'm assuming that you are using Month & Year as dimension...Is this right?
The set analysis is computed for the whole chart, not for each line of the chart.
If you use a filter on "A_dimension" in your Set Analysis and your chart uses "A_dimension" as dimension, you set analysis wont be calculated for each value of "A_dimension" but for all your graph.
Use instead a "if" statement.