It was still a slog, but I fought my way through both paths. I just gave Beruka a hand axe, paired her with Camilla, and tossed her into the ninja room. They only lasted a couple of turns while barely doing more than scratch damage

Beruka was the star of the map, really. Taking out all the ninja gave her a C-rank in axes, allowing her to use this club I acquired from somewhere that reverses the weapon triangle and exaggerates the effects. The myrmidons in the penultimate room didn't stand a chance.
By the way, I discovered that the Hoshidan princess (whose name I can't remember at the moment) has quite a lot of special dialog. Battles against Azura (don't worry, she survived this time), Camilla, and Corrin all produced unique pre-battle conversations. Maybe Ellie would have as well, but she got hit with that hex staff and did not have the HP to survive even a single round against the boss.
Now it's time for Chapter 12. This looks...fun.