For counter team you NEED 5* Pink Miko. 100% to deal 3.5x def counter damages, she has super counter, +50% def for herself and an healing skill. She is the best 5* counter in the game and should be a priority for the next choose-your-5*-waifu-stone if you want a good counter team.
You can also try for girls like Tartarian Aster or Green Bristlegrass for counter+evade.
And give them Defend Rate Up as promotion ability. Higher defend rate means even more super counter. And more counter damages. And give them them the bests equipement in term of defense. Always.
Here is my counter team, as I used on Nidhogg raid boss phase or on raid bosses event:
Counter damages are insane and Pink Miko deals more damage with super counter than with her skill. I hope it can help you in your team building.