Gotten Flins C6, best build for high investment?

https://preview.redd.it/j4u2up0ld8ph1.png?width=958&format=png&auto=webp&s=46e613cebf9a426ed168eb70437de82b7cab0883

I've always been told ATK/ATK/CRIT is the best way to build him but I was wondering if anything changes at C6? Sort of how Cyno is ATK/ATK/CRIT until you get his signature and then EM/EM/CRIT is best.

I'm currently running him with Alyosha (C6/Noblesse), Ineffa (C0R1), Columbina (C0, Fav Codex).