From so many threads that have been repetitive and never get anywhere due to argument.
I would like to sum up the objective of each group:
Hardcore demand : a challenge content, that is actually hard. Something that feel like achievement because not everyone can complete.
Casual demand : a challenge content that require low time consuming to clear. They believe to have player skills from all kinds of other games they used to play and don't mind a hard content, as long as it doesn't take too much time to complete.
SE demand : a content that is time sink for player to continue playing.
Let's make this good for everybody :
What about a challenge content that is not require so much time to complete, but very hard that not everybody could beat to let hardcore actually feel like achievement? SE could get time sink goal via "practice" or "tries to win" instead of time sink from "days of repetitive to get drop" "days of waiting to get NM pop". This will make everyone happy.
The closest challenge I could have think of, from SE previous work, is secret boss battle in Kingdom heart (2-F-mix). It is a kind of epic battle that require player skill more than gear, and the actual battle doesn't take too long time, if you don't get time sink result from losing and retrying.
However, even if it is that hard, it won't be enough in MMO, eventually everybody will beat it soon with a few tries. To make it actually work in MMO, you have to add "teamwork" aspect into it so that if someone fail a little off, then the team actually wipe. (Ifrit allow too many fail, thus too easy) Considering this require perfect run that everybody must perform together would make this actually worthy achievement. The chance to perform perfect run together by 8 people will be obviously low, this allow time sink that SE need. And of course, for casual, they can win if they have skill, and never win if they just simply bad.
Note: I agree that due to server respond time, the hard that come from dodging won't be a good measurement here. SE need to come up with some other way to make up for this, while leave the dodging fest content to 2.0 when server is fast respond.