Good news, bad news.
Bad news first:
You aren't going to be able to dual-axis the map the way you intend.
The fix will take some manual data prep before working in Tableau, but it's not terrible.
I don't recommend the table join that you've done.
You can do it.
You will need to Union, not blend and dual axis, the spatial data for the custom polygons. Union ONLY the spatial data describing the polygons. You'll see in the attached excel file that we only have Lat, Long, Play, Point Order and Polygon ID. Then you will want to blend the associated detail data from another data source.
The geospatial data can be separate tabs in excel, or tables in a database, and then union-ed in Tableau. Example here:
So in summary, multiple polygons will have to be detailed in the same source/table, but differentiated by Polygon ID. Then you could probably blend in the related data, linked on the Polygon ID field.
Attached is how I re-worked the geo-spatial data in Excel (FirstMapSecondMap.xls) and a sample workbook with the polygons mapped. You'll have to data prep the related non-geospatial detail data into it's own source.
I've also included my mapping presentation workbook from TC2015. It steps through points, paths and polygons and what is needed in the data.
If this has helped you, or answered your question, please mark it as such so that others can find it quickly.
Tableau Online Deployment Advisor
Thanks so much. I will give it a try next week and report my progress.
Sent from my iPhone
This indeed worked for me. Thanks so much for looking through this.