I don't want to sound harsh or anything, but what makes those dungeons difficult is that most enemies abuse reflect damage. They already have high stats, which is not a problem as they are supposed to be high level dungeons, but if on top of high stats you add unbalanced reflect damage it's... ineffable for a lack of better word
It's just a friendly warning before you enter those dungeons. If you're a good alchemist, do some batches of reflect damage and restore health potions and you can tackle them at level 20/25
If you don't like enemies that resort to that kind of spells, you might consider not playing them.