Transitioning back to MMORPGs in general, what do we learn from the last few posts?
There are two ways to cater to as many players as possible: First, you can design a feature in a way that it appeals to as many players as possible. This is often called "catering to the lowest common denominator". Second, you can design a feature that adjust itself to appeal to as many players as possible.
This is a very important difference. If a static feature is designed to appeal to as many players as possible, it often appeals only to a minority and at best 'satisfies' the majority. On the other hand, a feature that adjusts itself to the players, can be fun for many or even all of them, without making compromises; especially, if it is compatible with the simulation aspect.
Dungeons that allow those players, who overcome challenges faster, to face harder challenges, is such an auto-adjusting feature. Static dungeons that try to appeal to all players, on the other hand, are fun only for a minority and at best satisfy the majority.
Space Invaders is the perfect example of an addictive and for a time highly popular game that rewards players with challenge alone. Unthinkable in MMORPGs. A MMORPG designer should probably combine higher challenges with slightly faster character progression.
Maybe it is even possible to use this idea on more than just the challenge level of activities?
Have a look at the newest Extra Credits video.