Reinhardt and Lyn reign supreme

Inheritance and Sacred seals are improtant especially for my none +atk Reinhardt and neutral Lyn - Brave Lady

In fact, Xander is not mandatory but I use him to provide Hone Cavalry

Reinhardt (+spd -def): Dire Thunder, Reposition or Draw back, Moonbow, DB3, Daggerbreaker3*, Goad Cavalry, SS Attack+3
Lyn: Mulagir, Reposition, Swift Sparrow2, Desperation*, Fortify Cavalry
Xander: Hone Cavalry is the only skill needed for this battle
Performing Azura can be replaced by any dancer, Shigure is recommended.

*is mandatory to this strategy

Set formation as I placed in this order, Reinhardt should be fully buffed.
Move Reinhardt to kill the Axe armor, he should quad the armor to death and dance him for reaching the thief on the top, he can kill the thief with daggerbreaker.
Next step, use Lyn (not Xander) to reposition dancer back and she should be in threat range of the remaining thief, then move Xander to continue providing buffs for the next turn.
The enemy thief will attack Lyn and make her HP drop to desperation range, in the next turn Lyn can one-round kill Ursula and the green mounted mage without being retaliated due to desperation but be sure to keep her out of threat range with the help of Reinhardt's Reposition.
Xander can lure the thief if it survived Lyn's counterattack (it may not if Lyn is +atk).
The remaining sword cavalier will be easy.

Brave Lyn

Xander

Reinhardt

Performing Azura