Lil Puddin
I want to make a team for AR defense. Not sure if that changes your opinion on anything.
I have a Ninian who will be be one of the three to have IP and Legendary Azura with Guidance will be on the team. Not sure who else to use. I'm thinking Ophelia, Mythic Hero (on dark seasons, and Duma when I get him for Anima), Sothe/Lilina. Legendary Alm (+ATK) could be an option also.
Aether Raids defense and arena defense are things... At least with Aether Raids you can see a replay of them, but they just happen. I still don't know how my defense team since forever manages to get any wins. The only thing that has changed and very recently so is that I promoted F!Corrin and Selena to make room in my barracks. The Selena who I re-rolled for -- worst idea ever, but I have trash taste -- way back who was +Def, -HP was merged into a +Atk, -HP one and the free, Android-only F!Corrin was merged into a +Spd, -HP one. So, four 5* units to make room for two more barracks space. Also, Catria, Palla, and limiting the GHB and TT units in my barracks to four copies only, but I digress.
Although I have Lilina and Meisterhardt on my Aether Raids defense team, I don't think red is a good defense or even offense color outside of specific units which on the offense, would include Lilina because of the existence of playable Surtr and most units having low resistance. Reds are the most numerous and Ophelia and Reinhardt exist who are very powerful, offensively and defensively. There's also legendary Tiki if you can get her moving. I am not an expert, but if I were to consider a red for my defensive team, I'd consider any of the dancers, but particularly summer Micaiah and flying Olivia; and Aversa, Celica, Idunn, spoopy Myrrh, Tibarn, and Zephiel.
Dancers are self-explanatory along with Aversa with what her Aversa's Night tome does: "At start of turn, if any foe's HP ≤ unit's HP-3 and that foe is adjacent to another foe, inflicts Atk/Spd/Def/Res-3 on that foe and bonuses on that foe become penalties through its next action", and being a GHB unit anyone can get. Celica and Tibarn are there to mess people up. People have come up with defense setups meant to get Celica to low health and that's what she wants so she can be in Brazen and Desperation range. With a few dancers and/or units with Wings of Mercy, Celica can go on a tear. The issue is how to get the AI to move or not get cheesed. Tibarn is a strong unit who comes with Sturdy Impact. He might not kill someone, but when transformed and with Galeforce, Lunge or Pass, and a Heavy Blade seal, he could screw up the offensive team with his unrestricted three movement.
Idunn, spoopy Myrrh, and Zephiel are all about bulk and stalling or even straight up counter killing. Idunn is tanky with 39 neutral base defense and 34 base neutral resistance and gets tankier if she gets debuffed or is not at full health. +Def and +Res are both superboons on her meaning she can have 43 base defense or 38 base resistance. This is also before factoring her default Fortress Def/Res, Def/Res+6 for Atk-2, and Demonic Breath's effect "At start of combat, if a negative status effect is active on unit, or if unit's HP < 100%, neutralizes penalties on unit and grants Atk/Spd/Def/Res+4 during combat." If you want her to be a wall, then you could give her Wary Fighter to prevent follow-ups, replace Fortress Def/Res for Steady Stance 4 so she gets a Guard effect in return for Res+6 which you could give her a Warding Stance 3 seal, or a Deflect Magic seal to prevent mages and healers from cheesing her. Deflect Missile if you feel she'd be encountering physical ranged units more. Myrrh is just spoopy. Distant Counter and Special Fighter is apparently obnoxious on her. I'm guessing to go with Glimmer so she can counter with it or with something else if you want more damage, but like Idunn, she's a dragon, so she's targeting resistance. A Quick Riposte seal would let her close out enemies if needed. Zephiel has high bulk in general where his resistance can be made up by stacking unique refined Eckesachs for its Distant Def 3 or you could give him Barrier Blade and stack resistance. And like Aversa, he's a GHB unit where players who have been around for a while, he could also be easy to get to +10.
That's just what I think and any unit can be cheesed. The setup also matters as you can't just throw your "strongest" units and hope to win. If anything, the things you and others struggles with like Vantage units might be the thing you might want to incorporate. For instance, a lot of people use Eir for the scoring boost as she's a light mythic hero. It's overkill because of him being an archer, but Jeorge with unique refined Parthia and and Vantage would be able to counter her and possibly even when he's not in Vantage range. Against mages, he will also take less damage as refined Parthia reduces the first hit by mages by 30% and with them being ranged units, he'll also get the Atk+6 bonus and you can just stack that with whatever attack boosting A passive and a Fierce Stance seal. Vantage units will get cheesed by units who can take them out at full health or survive their counter, but once again, someone is going to struggle against them. There's also something with AI manipulation using Rallies and the Restore heal which clears debuffs. I was never good at AI manipulation, so you're going to need to look into that further.
I think focusing on offense might be a better idea that defense. You need the points to go up tiers or stay in the tier and that might be easier than planning a defense team and setup. Here's a Serene's Forest thread on it:
https://serenesforest.net/forums/index.php?/topic/86982-aether-raids-offense-team-unit-building/.
I could possibly... +5 the both Sothe and Lilina? I need 80k feathers and grails (eugh) for Marisa and Aversa when she comes back this weekend.
This is just me and I think using grails to use limited units for their skills isn't a good use of resources. They do offer good skills, but grails come by slowly and there's an arbitrary limit of 20 copies you can get. I'd rather just do a merge project or make a stupid defense team with them than kill off them for skills some of which are inexplicably still not in the regular summoning pool like B Tomebreaker.
Not sure about Sothe and what dagger he should use... There's Barb Shuriken and The Cleaner which come to mind. Sky Maiougi is an option and maybe Ouch Pouch. Game is so overwhelming after being away for 1.5 years.
It's up to you what you want him to do. If you're stacking attack, then daggers like The Cleaner, Ouch Pouch, or the effective against type daggers would be good. The others would depend on if you want him to be more of a debuff, support unit or an offensive unit that can debuff. I asked a similar question, but in regards to +Atk or +Spd for Sothe and Kagero:
https://serenesforest.net/forums/in...thread/&page=618&tab=comments#comment-5432157.
Barb Shuriken I don't know would be a good dagger for Sothe since he doesn't really have the defensive stat for a special to scale well from. He does have the attack for Draconic Aura and Dragon Fang, but Lethal Carrot might be a better option for the +10 guaranteed damage when he activates a special in which case, Glimmer and Moonbow would activate more frequently and Luna would be pretty strong. From what I remember, a Killer weapon and Luna is weaker than a Wo Dao weapon and Moonbow.