Are you guys on the beta? Because that should be fixed, I don't remember seeing anything like this in my multiple games.
Only named mobs in the beta. Fought a named Swarmy quest mob on level 3, and 3x named Thrusties on level 2 (2x Monster Zoo and one independent.)
Oh, that's a feature then. It's always been that way, you can get named monsters a level or two higher than the floor you're on.