I think many people agree on the following:
Dying from a bad roll is annoying as scoring a lucky hit is rewarding, not everyone's cup of tea but, in general, RPG/roguelike players love this.
Dying on a new encounter is expected.
Dying on a new encounter without learning anything to improve your chances next time is bad (so randomisation on damage should be kinda limited)
Replaying areas without learning anything new is grinding; not fun.
Given the above, permadeath on a large-scope roguelike doesn't work quite well, unless you have unlimited time for playing the game or you can present a refreshing, learning and rewarding experience each time, which is easier said than done. Not everybody has so much time though, and given the large number of good games nowdays, not many will be willing to devote all of their time learning the quirks of the game -- unless it's REALLY that good, which is not often the case.
An additional idea for larger-scope roguelike:
- The start of the game is difficult, no hand-holding for long, make it interesting and challenging. If you die, so what, you didn't play that much yet anyway and clearly have a lot to learn.
- After reaching a certain level/area, unlock character creation and start at that area at an appropriate level. These characters should be inferior to a well played character from the start of the game, and should be expected to die often. As often as characters in the beginning of the game. You can die with these characters a lot trying to find out nuances of the monsters/traps/etc of the new areas and when you feel comfortable, you start a character from the beginning and try to beat the starting and the unlocked area.
- This can be done as many times as needed, so for 50 dungeon levels you could have start points at level 0, 10, 20, 30 and 40.