Experimenting with the 4.3.1 release candidate locally shows that this issue of the aggregate -> sort query running slowly is fixed in the RC.
Do we have any idea when 4.4 will be available on General Release? Are we talking days, weeks, months, years? Any insight you can provide would be very helpful to us, otherwise we are going to have to look into either re-working our queries or look at other solutions.
Neither of which fills me with joy.