You forgot about Kilik and Maxi.My (very humble) two cents:
Top Tier: Ivy, Azwel, Siegfried, Mina, Mitsu, Zas, Raph, Geralt, Amy
High tier: Hilde, NM, Cervy, Asta, Xianghua, Cass, Sophie, Taki, Tira
Mid tier: Voldo, Groh
Unsure tier: Haoh, Setsuka, 2B, Talim
Edit: For the record, I don't think anyone is unviable in this game. That said, I feel like characters in High tier are generally designed to run offence, which I don't think is adequately risky considering characters who have more defensive/counterplay styles dont get rewarded the equivalent of in damage for guessing right, thus losing the damage race over longer periods.
Though I do agree that Yoshi is hella strong. He is nutty when he gets up in your face topped with his ridiculous RO game.