He's not over his head in AA, he's just struggling. He's walking some, he's not striking out at a ridiculous rate. My guess (not having seen him) is that pitchers with better command are getting him to make weaker contact by pitching to his weaknesses. It's a good lesson for him to learn to lay off hittable pitches that he can't do much with.
But as long as we're not talking sub .200, striking out 40% of the time type struggling, I think it's good for him.