Originally Posted by phu
There are three end game tiers after the main story mode. None of them involve running through the story again. Didn't want to do that because you already do that with all the many different characters, so we wanted to distill the higher difficulty modes into a more compact package.
Each tier has quite a few different areas that can need to be unlocked before you can progress. Some of these are kind of like distilled-boss runs through areas similar to what you saw in the story, but at a higher level. Not only that, but they come in different "challenge" levels where the enemies are much harder than normal but the loot and xp is much better, all of which needs to be unlocked (to be clear - unlocked in-game not via store). Others are very different and involve new game modes entirely, and they too have different challenge levels.
We're still working on it actively and iterating, but, the system as a whole is promising. Beyond that, there are tons of plans to add even more things post-launch.