The always thoughtful Rohan at Blessing of Kings has a great proposal: equalising gear in levelling dungeons the same way it is (as of 7.03) in PVP:

The problem is that leveling dungeons need to be balanced such that a group of new players in quest gear can complete them. But if one or more heirloom characters are present, that balance goes out the window. I think stat templates for leveling dungeons would be a great idea. Everyone would be reduced down to an even playing field. Dungeons would be a proper group experience once more. I rather doubt anyone will sheep anything, but maybe it could happen.

Despite the fun of tanking in heirlooms, this is a very worthy idea. I especially like the idea of cc returning!

I remember using Distract to sneak past mobs in dungeons once upon a time, and trying not to hit the sheep with AoE. Another idea for the mooted ‘Pristine’ servers, perhaps, though given they’ve done it in PVP why not implement it into PvE too - the tech is there with the Timewalking gear scaling. This would just be scaling as you level, rather than scaling down from max.