That KB article is very old, that was an option in version 5, before custom table calculations. While that method still works in some situations, I would not consider it ideal in any.
Also you have an interesting situation, with multiple mark types, where one of them uses the color shelf, and not all possible colors exist for all stores. That combination requires consideration for a number of factors that effect table calculation evaluation. To use a table calc filter in your situation would require a few complexities.
Instead, just make use the Top N Filter. Simply place "Store #" on the filter shelf, and from the "Top N" tab, select your top/Bottom 10 based on the Avg of "Time", and you will get two worksheets with what you have asked for.
If you need additional filters, you will want to be aware of the order of operation in Tableau, see http://community.tableau.com/message/139603#139603 for more details.
As you mentioned I do need to be able to filter by Region/District, and using those filters as "Context" filters solved the problem until I put them on a Dashboard and have other graph filter the Top/Bottom 10 using actions. Seems like actions are on a lower priority level for filtering even does fields are "Context" filters.
Yes, action filters only exist the category "3. General Filters on Non-Aggregated Pills" because actions only work on non-aggregated dimensions.