Horse Emblem...you better run

More or less is like my Effie

Many horsies will survive that tbh.

I mean....she cant really tank blyn or rein without heavy team help. If going the vantage route id go with ta over close counter so she can tank rein then have an ignis ready to nuke anything or just vantage blyn

No one sane will ever run a full team that can't check particular threats.
Or they'll do but burn 20+ Swords to get their deathless run.
I prioritize consistency over gimmick when i do my runs and it all goes really smooth, same goes for my defense.
So, instead of focusing on SI and investing quite heavily on subpar meta checks I can promote 4* with good IVs, get some relevant SI done.
One trick poneys dont work on the long run. Same goes for defense, i happen to score 30+ on the simple fact that people quit when their deathless is ruined, I won't invest heavily on something handled by the IA.
Your F!Robin is cool, your Effie IS cool but they won't stop my deathless, sure it might screw my rein but it gets properly rekt by my Sonya

Tl;dr stop thinking you're building OP units when you invest 100k+ and rare skills in an unit that won't pose a threat to any decently built team.