I didn't, but I picked Magic for my dump stat anyway. :/
I was getting tired when I retried that one and did the cheap way out of deploying myself and Camilla, then just having her blitz me to the escape points. I saw ahead and kept a save on 21 since I'll probably feel like doing a legitimate run tomorrow. 22 isn't nearly as bad, thankfully, seeing as I got most of the way through half-asleep using characters deprived of Chapter 21 EXP, but panicked when the reinforcements in the top corners caught me off guard.
While I'm pretty sure you mentioned dialing the difficulty down to normal, I'm going to concur that you don't want to be skipping EXP. I could tell right away that this is a very finely balanced game with clear designer intention behind every decision, so if you cheese a mission and wind up not gaining any experience, you'll go into the next mission weaker than the Developers intended, that little bit of weakness is going to catch up with you, and you'll have some problems, which will cause more problems, and it'll snowball until you've backed yourself up into an unwinnable game state. And neither you nor I want to see that happen.
So yeah, go back, throw yourself at 21 again, place some thought into how you can evolve your strategy to overcome this new obstacle, and if you're still having trouble, report back and I'll dispense some more tips. God knows I had to pull out of the mission entirely to go back to the Castle and do some very special preparation just for this mission.
In other news, I got Benny's Son's Paralogue mission, and it would seem I married him a little later than intended, because the level adjustment on enemies for difficulty bit me in the ass pretty hard. Benny's Son is placed deep in enemy territory and surrounded by enemies that badly outclass him, and he can survive, at most, 3 turns. Cut to my tenth or eleventh attempt as I bumrush towards him to save him from his fated curbstomping. Good news, I did manage to save him and complete the paralogue, but not without a lot of hair pulling and frustration.