Are you ready for madness? It took me 3-4 stamina pots to do this. Nino had to learn Escape Route 3 and Azura had to learn Sol, just to survive. She also learned Def+3 instead of the Spd+3 she uses, but then she no longer could double the red cav and also the Firesweep Flier moved to the right side of the red Cav at the 2 minute mark instead of behind, so she would have died the next turn.
Anyway, for those interested:
Azura (+Spd/-Res)
Cordelia (+Atk/-Spd)
Nino (+HP/-Def)
Xander (Neutral, but level 40+1)
I am not sure how many of my inherited skills are really necessary, but I am cutting it really close at some points. Cordelia needs to be +Atk or she can't kill Valter. Azura needs to be +Spd or she won't double the Red Cav. Anyways, maybe it helps to give you at least some idea how to do this map without an Archer or Reinhardt.