Well what I honestly believe for these well-balanced, popular roguelikes (Crawl, Adom etc.) is that if you died because the game generated something too strong for you, for example Sigmund, and you died with a unidentified scroll in inventory...well that might've been a teleport scroll! Also, why does people specifically complain about Sigmund? I consider myself a 'noob' in Crawl, but I rarely die from him. If I do, my character was level 2 or 3 and I don't really give a damn about that extremely unlucky death.
If roguelikes had save/load function like most other games, noone would be complaining about difficulty. Because even after dying 3 times in the same situation, the fourth time you'll discover something you DIDN'T try yet, and survive/slay your enemy. And this is what I'm getting at. I find it very rare for a decent character to die, and me thinking after: "WHAT?! That was impossible!!" I mean.. perhaps it WAS impossible, because I was stupid enough to walk straight across an open big area, after having used up all my healing-potions earlier on, in an encounter I over-estimated.. And perhaps I forgot about evoking that staff of paralyzis.. I mean, there's almoast -always- a way out. It's just that you only get -one- shot at estimating what it is, then being successful.
I find most my games I do hundreds of correct decitions, then one mistake..
Which ofcourse means it IS difficult to win.
Roguelikes are -DIFFICULT-! If you encounter a roguelike that isn't, it's probably a boring game. I believe this topic didn't start about a debate whether RLs are difficult or not, but someone asking if some games were just -impossible-. I have never won a roguelike
But I know they aren't impossible.. and I know that for each 10th play atleast, I've gained more game-experience, and my new characters tend to do slightly (if not remarkably) better. The better you get, the better your characters get, and the more the experience of dying costs..
To say something about how hard ADOM is.. Thomas Biskup said in his interview here at ToR that he never got past level 20 in ADOM himself..! XD
However, it is not impossible! =)