Round table

I think the issue here isn't the level, but the quantity. The value of a 5th-level dungeon is 5000, and a minor artifact is also 5000. That's a total of 10,000. This is similar to the defense of Utopia. And Utopia would be guarded by approximately 10 monarchs, not 16. The conclusion is that the artifact is used by a generator for some kind of seer's hut in a quest, which is why it has a higher value, and therefore a higher total defense.

Are there quest-specific minor artifacts?

On the other hand, Valentin asked a good question. I just generated some maps, and quest artifacts are of the "treasure" class (art1), while the Blackshard of the Death Knight is of the "minor" class (art2).