@XRay I did it on Abyssal! It took me 40 minutes though. I didn't record it, unfortunately. I used NY Azura with WoM, NY Camilla with Firesweep/Drag Back, Catria with Fury, Desperation and Galeforce, and Est with Iceberg/Drag Back. I used Camilla to drag the armor back in the beginning for Est to kill. The rest of the map was using the Whitewing sisters to triangle attack things and Catria to either kill more or run away after proc'ing Galeforce.
I needed Azura to run to the other side of the bottom right corner with WoM where she tanked the cleric. Camilla with Ward Fliers protected Est from getting killed by the cleric at the end, so she took the damage and barely survived. Est killed Marth and the last cav.
So frustrating! I should get a free Legendary Marth for this :(