I just completed all the Shiyu stages using my Caesar, Burnice, Piper, Gunboo, and Koleda, Lucy, S11, Rocketboo teams. None of them are fully maxed except Piper, but I finished all the stages at S or A rating. The last stage is hard to S because the enemies hit to hard and I don't really practice dodging their movesets, but definitely doable if I decide to spend an hour on em.

My most powerful character is Piper at C6. With Burnice's skill, Disorder triggers all the time.

However, the S11 team is a lot more fun to play because you need to use all the dodge and parry mechanics to succeed. Caesar trivializes defense.

Nekomiya just totally fell off. I'm thinking of pulling for the next electro anomaly character, but I already have grace, so I dunno.