Well, since no one seemed to reply to this I might as well try to give some advice.
Dang it Kelekod, why did you have to start writing an answer when I was in the middle of giving one.
For Alfonse, you don’t want the +Eff when refining his prf since it locks him out of fighting blues, which he can do quite well. +res (what I use) or +def help him to take hits and get into brazen range better. Alfonse works amazing with Brazen stacking because of his prf, Brazen Def/Res from 5*ing a MKana is what I use for mixed bulk, but Brazen Atk/Def from Ares is really cheap and effective. Brazen Atk/Res is a really good S slot for him too. Brash Assault is really cheap and combos surprisingly well with the brazens because he won’t need speed to double and he has enough def/res to take a hit. Atk Smoke is always an easy choice for the C slot since it helps with taking hits. Special can be whatever you prefer, bonfire is consistent damage with a not too long charge, ignis has one more charge but for quite a bit of damage and luna helps him shred through units that defence stack. Go with any assist you prefer, but I should mention that rallys improve scoring.
Sharena likes stat stacking as well, but with bonds since her refine is a bond. Any bond in her A slot for for whichever stats you want to invest in her works, personally I went atk/res in the A slot and spd/res in the S slot.
As for a B skill, Wrath from Astram is really strong, but if you want to invest a bit higher later on with Blue Flame, I’d wait to fodder an Owain for both. Renewal works fine and helps keep her healthy without needing team support. Again, Atk Smoke is a good C slot that helps her take more hits. The special is ideally Blue Flame from Owain since it comboes with her bonds, but it can be a bit expensive so Luna is a good option otherwise. Assist is whatever you want it.
Anna is the hardest to build since Noatun doesn’t have a definite role in helping her or her allies. Personally I scrapped it for Wo Gun from Libra since it helps with her low attack, but if you want to stick with Noatun you could try making her a sort of support bot with spurs in the C and S slots and a rally to help buff up her allies. Her A skill is a bit hard to work with because of her mixed bag stats, but Fury is an easy option. Anna arguably needs Wrath the most because of her low attack, so if you want to fodder of an Astram to anyone, Anna is a good choice. It comboes with Fury, but if you find it too expensive Renewal works as well and helps offset the damage from Fury. As always, Atk Smoke is a strong contendor for the C slot, helps her and her allies take less damage. Moonbow is a good choice for her because of it’s short cooldown and it helping her deal damage consistently, as well as letting her deal more damage with Wrath or Wo Gun if you give her either of those. Assist is preferential, again.
Should mention that I’m not finished with all their builds yet, haven’t made them “optimal” quite yet since it’s a bit expensive as far as fodder goes.