Grim's Grotto is the only Hard random dungeon that we have. The thing is, it's way too gimmicky. It uses a much more random spawning algorithm that regularly creates unwinnable games. After three starts in a row that put me in a closet blocked off by level 4+ monsters, the novelty wore off and I found myself wanting a Hard random scenario without the practical joke factor. I'd even settle for Venture Cave being given a toggleable Hard setting if need be.
Probably wouldn't be too hard to throw one together. Just create a variation on an existing dungoen and bump up the monster stats, maybe change the tileset, and ensure it has exactly one random boss. Up for it, devs?
Still, difficulty sliders could be very interesting. Especially if there were more than one way to increase or decrease difficulty. Like for exp: Easy (old algorithm), medium (current algorithm), hard (current algorithm, +1 exp per level to level), extreme (bonus exp -2, +1 exp per level to level), AVATAR (no bonus exp).
Boss spawn [x] First boss can be normal boss [x] First boss can be special boss (directional dungeon bosses) [x] Spawn second boss [ ] Second boss can be normal boss [x] Second boss can be special boss
Extra Dungeon Rules [ ] Extra gold value [ ] Extra Glyph spawn [ ] Extra Boosters spawn [ ] Items on ground (Hobbler's Hold style)
Extra Monster Rules [ ] All monsters gain Cowardly [ ] All monsters gain 1 Death Protection [ ] All monsters gain First Strike [ ] All monsters become Undead [ ] All monsters gain Knockback [ ] All monsters gain Curse [ ] All monsters gain Fast Regeneration ...
If I were to make a "real" random hard, I'd probably rework Grimm's instead of adding another one. Fact is that if Grimm's isn't good enough for people, it would be silly to keep it there and add another dungeon.