So, they have Impossible Dillema to solve: challenging hardcore that plays and plays and have almost no new challenge and criticizes the game because of that (vocal minority, check the trophies stats and see) or to allow casuals and newcome players to have some progress without timesink.
The funny thing is - the game DOES have enough content, just not how they're using it. If they made the following changes the game would be a lot meatier:
* Tie drop quality and rarity to enemy level. Enemies above player level drop rarer loot. Enemies of lower level drop more common loot. Gray enemies drop no loot, only ammo.
* Auto-scale lower level players to the highest level player in the fire team. Friends can always play with friends, no matter what.
* Auto-scale enemy levels to the fire-team level. All missions become available to play, at all levels.
* Always drop loot appropriate to the character's level (not the upscaled level). Players will always get level appropriate loot.
* Once a mission has been unlocked by a player, it can be replayed any time, at any level. Guests can access higher level missions the fireteam leader has, even if they haven't unlocked for that player yet.
* Open world / shared spaces should use matchmaking to put fireteams of the same level ranges with each other. Low level players will be matchmade with other low level players and vice versa. This means patrol missions will always scale to your level.
Boom. Its the Diablo 3 post-launch fixes formula, but I think it'd work. Destiny would have all of its content available to play at all times which would help with variety and the grind. Bungie could still put up bounties and dailies and weeklies the way they do now - picking select missions and setting skulls on em.