Herrick is drunk because he is over the B.S. The purpose of this scene was to show how differently people act when intoxicated. The tone of the scene is a bit aggressive because the prisoners are giving him a hard time.
This character does not fulfill the characteristics of a tragic hero. He is not good to his people and he does not save anybody. Instead he treats them unkindly and flees his kingdom. Even though his story is tragic, I would not consider him a tragic hero.
