Things like HNMs are awful time sinks that result in wasted time while you could other things. Not to mention as Enkidoh mentioned Shikigami Weapon and other NMs like that. While I'd like 1 or 2 open world Dungeon zones, I'd prefer to never see open world NMs again. One fair solution might be for NMs in instance dungeons. Perhaps a monster that has a 25% pop rate in runs (it can't be obnoxiously low, but rare enough that it's still special). Either it pops down an alley people don't always go down, to give more reason to fully explore dungeons, or have it replace something in the normal trash set, but should still be avoidable to account for increased difficulty. The Deep Jungle Coeurl in Long Stop already kind of sets the stage for this since it guards the level 30 class rings.