Hopefully they have the ilevel requirement high enough to ensure some semblance of competence in the groups that are randomly formed.
Maybe they can extend this model to heroic dungeons as well. No idea why they're doing this weird flip-flop thing where heroics dungeons are piss-easy, but heroic scenarios (at least, as of now) are semi challenging. They can just make heroic scenarios and heroic dungeons on equal difficulty levels, and leave normal scenarios and normal dungeons as the filler.