Well, this is D&D General - so I can't speak to 5e D&D (though
@Imaro quoted something upthread that seemed clear enough), but can speak to 4e D&D. It makes the tiers - Heroic, Paragon, Epic - crystal clear, and follows through with power design, ritual design, magic item design, monster design - all of these cohere with the conception of the tiers.
Published adventure design, on the other hand, does not always cohere with the tiers. I started a thread on this back in 2011:
Scenario starting points and PC's position in the gameworld