We have the same problem, all worked ok in 2012 but not in 2013 & 2014. At the design stage we need to know and tag the flow velocity at each part of the ductwork, as it is critical to our design for ductwork in public areas of themed attractions.
Currently I am creating new tap's that are based on the design of tee's as these do not give the 'multiple values' problem. Not an ideal solution but a workaround to replace the removed Revit functions.
Schedules may well highlight the problems but at the early design stage these are not yet done and it seems to cumbersome to create and cross reference to schedules.
The function was removed for the 2013 version and will probably never be returned. Possibly Autodesk should consult with designers and take note on site of the way buildings are built, in many other areas as well.
We still create our main working drawings in AutoCAD. Our use of Revit is 'forced' in some of our contracts, and we have to use the version of Revit that other consultants are using. So, even if the problem had been fixed in Revit 2014 we would still be saddled with software that is not up to scratch.