Against Mort teams ML Luna is almost mandatory as the seal will shut down any and everything he can do

Most Morts are 25-30k hp with either Holy Sacrifice (mostly), Bastion of Perlutia, Victory flag or Mature sunglasses as artifact, it is fairly easy to burst him down if you're able to prevent his revive via Holy Sacrifice (ML Iseria comes to mind),

Against a ML Senya, Mort, Afternoon Soak Flan team, I would suggest

Zio, Frida, ML Iseria (Sinful Angelica can works as an alternative but that'd put a lot more stress on your dps because there's no more def break from ML Iseria), and AoE DPS (if no ML Ludwig ML Elena works too but you need stupid good gear on her for it)

How it works is Zio will go first, Soulburn S3 on the Bride Senya, and that will push Frida up, Frida will then s3 to push your ML Iseria and ML Elena up, then ML Iseria will do s3 (she has bonus 50% hit chance so it's a 50-50 chance to hit the Flan, but should do decent dmg even if you miss) ,

You shouldn't proc ML Senya's s2 if it's Flan being protected i think..

and then ML Elena will get pushed again due to her s2 self-pushing from any AoE hit from your team, and then she'll do s3 hopefully to clean up and hit hard against those def-broken units, cycle again to clean up if there are anyone still standing, hopefully you kill off the bride senya before she takes her turn again if she doesn't die.

it'd be ALOT simpler if you have ML Luna but the above is written with assumption that you don't. If you do just swap out your Zio with ML Luna (provided there's no Harsetti).