The POWER....of Love

Ike uses his base kit well, as most of the enemies on all the maps will carry 1-2 sword units, so sword breaker + heavy blade works wonders. C slot is hone speed to help Soren, while seal is +1 Attack for that extra bit of damage. Can 3RKO the Black Knight, but has to watch out for Black Luna. Use the other enemies on the last map to build up aether, and then proc when Black Knight initiates attack to follow up with sword breaker.
Soren also benefits from boosted stats, a +SPD Soren reaching 50/40 (with s-support Ike). Plus, he supports Ike well with pesky blue units that appear Mid- and sometimes on the final map. Replace Watersweep for Desperation.
Azura is standard singer, and mainly deals with dragons where Ike cannot, but can be used well against Black Knight with her own Luna.
Celica is the breath of life healer, and she helps with red mages/other bulky units where Ike would take longer to KO, so mostly a support role this time around. Also have desperation, because she can kill certain reds/greens that Soren cannot S-support with Azura for multiple synergistic wins.

Ike

Soren

Azura

Celica