There are a few different ways to handle "rolling down". Part of it is the loot system in use, and part of it is the general temperament of the players and officers, and how they specifically view loot.
I can only tell you how our guild looks at it:
It isn't fair to roll against a clothie, when the clothie can't roll against you on your armor type.
There are, of course, counter-arguments to this. But our guild tries to de-emphasize the whole "BiS" thing, because while it may min-max your toon, not wearing BiS doesn't utterly wreck your gameplay. And of course, since skill>gear....
That's just my take on it, is all I'm saying.