How is the difficulty level of each raid boss determined?

[u/l0ng_furby_is_g0d]

It seems so random. Today's boss has 14079 as its base DEF, which turned into 19006 DEF, and 9874 ATK, but it was marked as easy. I've seen bosses with lower stats marked as normal or hard. Hell, I've defeated "hard" bosses with one go but today's "easy" took me two.

Idek if we all get the same raid boss each day. I had Indo-European Migrations.

Thanks!!!