Pretty much every game, especially MMORPGs, develop a community that is barely able, but still able, to consume the majority of the content. Its the game training its players, rather than the other way around.

Harder games make better players to a large extent (there are limits to this, obviously. But look at the level at which the average OW or LoL player plays his chosen game: People are pretty good in the mid-ranks already).

24s that are more difficult (World of Darkness, for example) and require you to do mechanics because you will wipe, every time, without fail, will train players to play better, because they HAVE to.

Unfortunately, almost regardless of how easy or difficult something in a game is, you will always have those whose limits of playing skill (whether actual skill or, more usually, the will to try actually playing decent) are just below the current expected cap, and thus they feel uncomfortably stressed when trying to stretch up to the expected skill level to get their shinies. And they will complain.

Basically, in any game, nothing is ever easy enough, yet still fun. There is no sweet spot of "no complaints, maximum happiness". So, there is no point lowering standards to the point of content being boring upon release.

I think the wheeping city of mhach has the more interesting fights and mechanics, but numbers (and thus mistake tolerance) are a little undertuned. I think the Scathach is a good fight, the Cloud of Darkness was quite well-tuned at its release, whereas the entirety of the Syrcus Tower, Void Ark, most of the Labyrinth of the Ancients (exception being possibly the Behemoth) and the Diabolos fight(s) in Dun Scaith are untertuned.

I think we could do with a slight, but not big, increase in difficulty, or (actually better) a scaling down of equipment stats in the new 24s, but just use mechanics that you MUST do in order to succeed. People will adapt. We learned how to handle the skeletons in LoA, we learned how to go to the Hounds belly, to dodge the Cloud of Darkness, to dance with Titan Extreme, and to handle the Final Steps of Faith with weak gear on its release. We, as the playerbase, can be expected to stretch our legs a little more than just Dun Scaith.