You should be able to do this with a couple of minor changes to what you have in the example. I've attached a workbook with a very quick go at this - but confess to not having checked the answers, so please look carefully. I'm pretty sure that at least the principle is right, though, if not the detail. ;-)
The two changes address your two issues:
1) The sort order. If you define explicitly the sort order that you want for the Quintile calculation, you can have the view sorted by whatever you want. If you click on the Quintile pill on the colour shelf, select Edit Table Calculation and then go into the advanced option, you can specify that you want the calculation to be sorted by SUM(conversions). That is then independent of the display order.
2) If you want to filter the view without impacting the rankings, you need to define a calculated field which can be used to filter after table calculations have been applied. If you look in the attached workbook you will see that I've defined a field [Foilter Date] as defined below. This is a trick, to allow the filter to be applied after the table calculation.
[Filter Date] => LOOKUP([ATTR([Date]), 0)
The LOOKUP function is a table calculation. With an offset of 0 it just means lookup the current value of the expression - but as it is a table calculation, Tableau defers evaluation of any filters till after all table calculations have been evaluated.
Hope that makes sense.
Quintiles Practice RL.twb.zip 13.4 KB