Mythology skill is what ids monsters
{Senses & Intelligence}

Disease rats: By that point, curing disease isn't a problem with Alchemy or by actually learning Cure Disease, and if it is, one can just avoid the Monastery until it isn't a problem.

Secret Dungeon: Go in at a high level. By then, the Bishop has had a chance to become incredibly powerful.

Military Base spellcasters: There's Magic Screen, Element/Soul Shield, and summoned elementals are extremely vulnerable to status ailments. (They're a good example of low level/high HP monsters.) Enemy mages can often be killed by damaging spells and ranged attacks, as they generally don't have high HP. (Unless you're fighting something like Rapax spellcasters.)