As I wrote on Twitter today, Destiny's Heroic Strikes demonstrate how severe difficulty limits player options. The result is rote and redundant gameplay.
For example, when enemy weapon damage is exaggerated so that the player can only take one or two hits without dying, then the player is strongly encouraged to avoid risk of being hit and so starts sniping from a safe position.
Perhaps that is what the developer intends. The player might be challenged to discover and well perform that strategy. Such a design ultimately offers much less value to the player than a design that preserves player freedom. A rote challenge is accomplished once or twice with pride, then abandoned or otherwise endured with minimal enjoyment. Once conquered, the opportunity for proud accomplishment is past and never regained.
Free and dynamic experiences, with surprises and a variety of choices for the player, allow for repeated enjoyment of content. Both players and developers get more bang-per-buck by dynamic content.