I have some rambling to do, and this thread seems like an appropriate place. As someone who stopped playing this game a long time ago (will play again when it is finally released), I might be able to provide a different perspective to the recent discussions about difficulty.
I stopped playing at some point before class challenges and the allegedly crazy potion preps were added. I beat the Avatar and Namtar back then, the other vicious dungeons were added shortly after I quit. It took several attempts, I used terribly cheesy stuff (monk with huge resists and good damage, gnome warlord with nearly unlimited life protections, really old trisword that gave a huge damage but posed some inventory restrictions or something), and I beat them. But I simply couldn't have done it with most combos, no matter the preps or gods. Did the game get easier or harder since then?
Seeing how people are now talking about completing vicious dungeons with all classes, it must have gotten a lot easier, or maybe these players are just on a whole different level of skill (with the many additional months of playing this may very well be the case). Either way, to me the difficulty seemed fine back then. Vicious was a nearly insurmountable challenge, even hard dungeons felt really challenging. And yes, I needed to beat these vicious dungeons to feel like I had beaten the game. But I didn't need to beat them with all the classes. What classes you had completed a dungeon with wasn't even shown.
Back then I felt a bit sad to see that the notion of completion had changed between the freeware version and the beta. In the freeware, there were just a few dungeons, and you would try to beat them with all the classes, getting benefits for completing the dungeons, which in turn made beating them with weaker classes possible. In the beta as it was then, truly and completely winning the game meant (to me) "beat all of the very many dungeons at least once, with any class/race combo you want, and unlock all the stuff". This made class balance too important in my eyes, and would have significantly reduced the long-term appeal of DD by promoting always using the strongest combo instead of promoting using a variety of classes.
Now true completion of DD seems to mean "complete all of the very many dungeons with all of the classes". This makes me very happy, and addresses the concerns I had back then. But to me it seems like the recent discussions don't fully acknowledge the scope of this task. People seem to have done it. Maybe even done it several times. But this probably took hundreds of hours of playing to do, and certainly hundreds more to get good enough at DD to do it. I played the freeware for hundreds of hours, and then played the beta for hundreds more. And the game is much longer now. Few games have this kind of longevity, and few players are willing to invest so much time. "Completing" the vicious dungeons (by the above definition) is a task very few players are even going to attempt, and that's okay.
If people want to stop playing after a few hundred hours and move on, that's fine. People can, will, and should determine for themselves when the game stops being fun for them, and this point will be different for everyone. There is no one "correct" difficulty, there isn't even one correct difficulty ramp. I'm pretty sure DD is already in a fairly good spot. People who have been playing for years can only wildly speculate about how the game feels to an average new player. Most of these will probably like DD a lot less than the people who have been playing it for years. None of the input comes from truly new players, and none of it comes from average players. Of course DD should be the best game it can be, and no amount of fun should be considered "enough", so sure it should keep improving. But after reading the recent discussions about difficulty it seems to me like people are splitting hairs. Take a step back, look at the big picture, and enjoy.
DD was awesome when I stopped playing, and with the amount of improvements it seems to have gotten since then I cant even imagine how great it must be now. I'm looking forward to playing it again when it is released, and discovering all the new ways to beat seemingly impossible dungeons.
By the way, DD never stopped being fun for me. I just want to save some discoveries for the released version.