@HeelPhakdi
There is also the fact that they can take on even stronger monsters now. Even if her level doesn't drop, since it seems his magic does flat damage and not a range they can keep taking on creatures more than double her level. Sure, that would mean he would only go up by 15 levels instead of the 30 in the last fight but he would still level pretty quickly.
Honestly, if it were me I would be constantly spamming magic and item creation to keep my levels in the single digits if I found that feature. And I'm sure the title bonuses aren't affected by level, so I would also want to check to see if there is a title for beating a dungeon at level one.