Finally pushed through and recruited Amalia. That feeling of despair when I beat her squad after so many attempts and then that happened. Though it turned out that fight was much simpler after I quickly realized I just needed to drain her PP and then dodge her column attack.
I feel pretty good about doing it with level 20-21 units, though.
My team was Travis and Miriam in the front, with Yahna, Gilbert, and Rolf in the back. Travis guard sealed the front row (I'm not sure that ended up mattering), then Rolf froze them with Yahna's Ice Conferral, killing the wyvern in the process. Miriam killed the archer with Magik Attack, and Yahna 2-shotted Amalia with her ice spell. There was absolutely luck, because Rolf needed to dodge the mage's attacks to ensure I had enough people standing. Ended up 2 left on each side, and I guess I had more health or better status or whatever determines the tie breaker. Gilbert was mostly just there to counter the initiative drop at the beginning, but his attack boost maybe mattered for Rolf?
Then for the second part, upon realizing I needed to drain PP, I swapped Yahna out for Chloe (just because she happened to have that spear with the -PP attack) and Rolf for Selvie. Then upon realizing I needed a good dodge column, I swapped Gilbert for Ochlys.
...now I gotta fix my shit and hope I remember who had what and how their skills were set up. @_@