It's wildly different depending on what character you're playing, too. Some are just better-suited to EE play. I just FINALLY got my completionist trapper up to the point where she can cope with most eE content reasonably well by herself. My baby 3rd-life bard with NO gear ran an elite streak from 20-28 pretty much effortlessly. And it's not that bard is so much more powerful than my rogue--my rogue is a BEAST! It's that CC dominates eE and bards have that CC.
The challenge in the game doesn't come from "hard" content. Add more hp and damage and higher saves to mobs and within a couple of weeks everybody has adjusted and they're stomping the new content. Heck, even insane stuff like beholders spamming 30 con damage didn't prevent most people from running stuff. When it's just a numbers game, the human players win every time because the monsters are STUPID.
If you want a bigger challenge, you have to challenge the PLAYER. Most of the people I play with, regardless of uberness, cannot do the more complex Cannith challenges worth a ****. Eveningstar challenges are all about killing things, which EVERYONE can do. But to move efficiently, plan a route, recover from setbacks, keep situational awareness, set priorities, react to changing circumstances . . . the vast number of players simply can't hack it. Which is why the difficulty in the game seems to be devolving into "kill all teh things". But killing stuff is really only a challenge when you have no clue how to play your character advantageously. It needs more layers than that to challenge the player. Some of the hardest parts of the game are really pretty low-level. Fighting Barnzidu in A New Invasion. If you can't pay attention to those exploding plates, you can be the Uberest Uberer of Uberdom and still get your butt handed to you. Doing the shield chest optional in Ghosts of Perdition. That ain't no picnic. Heck, 6-starring ANY Kobold Island challenge. Bleh.
The challenges exist in the game but people avoid them because they're a huge pain in the ass and you need SIX people who KNOW what they're doing. Three of them can't just fart around doing random stuff, not communicating, not following instructions, not using their judgment and succeed. Judging from the way most people play, "carry me" is in fact THE preferred playstyle.