I hate it when people spew this BS.
The RDF is there to make finding groups reasonable. Anybody who played back during Vanilla, TBC, and Early Wrath would remember how much of a PITA it was to form groups manually, and it is also why a lot of people never touch the M+ system whatsoever.
Manual Groupmaking is not really a viable thing if you want a group anyday soon.
What they need to do is shuffle 80s into their own groups and 10-79s into their own bracket so that people can have fun, though as another poster suggested, Level 70-72s wearing 460 are also a rather ridiculous problem in dungeons, especially if they happen to be WW Monks lol.
They could get around the 70-72 thing by scaling them down a bit if they are over X item level (make them behave as though they were wearing 420).