In many cases, the data being represented on size or color is comparable across multiple marks cards and worksheets. However since tableau does not allow dynamically synchronizing legends, the results may be deceiving. Complex data transformations are required to achieve visualizations that properly communicate the information shown.
For example the following dashboard shows flight paths in the US. There is a field for origin city and another field for destination city. Boston to Newark is the top flight path route with continental airlines. If you wanted to see which other cities are connected to these, an easy way is to apply an action on origin and destination to 2 separate maps. However the results are very deceiving as the size does not show that continental airlines has 7 times more flights to Newark than out of Boston.
The workaround is to pivot the data, which in this case requires custom SQL and duplicates the number of records from 144 million to 388 million. This then allows an origin/ destination field indicator to slice a single map into multiple maps.
Another example is when comparing ratios or averages across a number of different levels. You may want to see how the profit ratio by county compares to the profit ratio by state. However the view below is again deceiving, as the worst and best states have twice the profit ratio of the worst and best countries.
Fixing the axes in a static manner is not a good solution, as the legends then do not respond to filters.
Thank you for considering this request!