This game needs Savage solo content and Savage 4 player.

[Nestama]

The 29th Masked Carnivale is kinda what you're asking for, but it's BLU only (and you need certain spells to make things easier/clearable).

Rathalos Extreme (sync'd) is probably the closest we've gotten, but he's only hard because of the 3 KO count. Pharos Sirius (before it was nerfed) is probably a close second. I recommend running that dungeon with minimum ilevel turned on

I honestly think that it's because Pharos Sirius was nerfed (which was because people found it too hard and would leave it immediately if they got it in Roulette. Wipes were frequent on the first boss alone) is why we won't get any difficult 4-man content.