The demon lord's elite four have two dummies, but Calby is a little smarter than Guren.
It is heavily implied that Ardios and Rubert have some sort of connection. Maybe Ardios personally knew the previous hero/wielder of Rubert.
It was obvious that meathead Guren was going to challenge Laura for a duel, but Miria gently reminded him that he was grossly overstepping his own authority trying to start a fight with a new comrade. He really is dumb for not considering her strength, when a stray attack from her almost deleted him if not for Calby saving him.