However, the "end game" piece is the piece you'll be playing over and over again forever.
Because next week, the raid timer resets and you'll do it again. And the next week, again. And in-between, you'll be doing Strikes, Daily Quests and Weekly quests to fill time (and farm reputation) and get new items.
While the leveling up part, you'll do, at best, 3 times: one for each class.
That's the thing that most people don't get about MMOs And destiny (even though Bungie keeps saying that it's not an MMO): The leveling up part is not the important part. That's why "the game only really starts at level 60" say exist: The raids are the cool part of the game, not the leveling up to them.
Not only that, I believe that Destiny is not a "loot" game, like Diablo is. It's not a "every run, I'll get a million drops, and every will be 1-2 points better than my previous weapon". Destiny is a "farm reputation and exchange items/rewards for loot at the vendors" kind of game. Further things that made me believe in that: There's no Loot Trading, there's no Loot "rolling" (Needs/Greeds for unique loot that every boss sells). Most of the things you get out of the game are materials, or trash loot that you turn into materials, used to upgrade the good weapons you'll get through reputation rewards/Buying them from Xur through strange coins, which you got by doing the Strikes/Weeklies/Dailies between each raid reset.
It also sounds "a drag" because there's only one raid for now - which is a good thing: I also believe that the larger percentage of the user base on this game doesn't know about raids, and having one to learn the ins-and-outs of this type of gameplay will, imo, benefit everybody.
Now, the real question is: Will the new raids contained in the DLC be as good as this one, but different enough?