So yeah... since I didn't use either of Noire's parents, I'm running into the wonderful issue where she can be oneshotted (not one-rounded, killed in a single shot) from anything attacking from outside, and it all doubles her: the longbow snipers, the reinforcement sages, and the reinforcement Mire sorcerer (well, Mire users can't double, but he has a OHKO at 80% displayed hit). Didn't use Kjelle's either, but she doesn't seem to have reinforcement issues as far as I've seen. Cynthia and Nah can hold their own (the inside enemies tink) since I did use their parents.
Welp, time to level Tharja and Gaius a bit I suppose. Seems to be my only choice aside from just bodyblocking every stairwell within ten tiles.