I totally agree with Xynian and I can't say anything about Sayu and Sara, but I think Rosaria and Yanfei have their niche in which they work extremely well. Rosaria in particular works better as a sub cryo dps than Chongyun: sure, Chongyun's burst hits harder, but Rosaria gives a crit rate bonus to the whole party and her burst applies cryo constantly (which is great in freeze comps). Chongyun helps better as a support when C2 and provides a - 15% bonus to burst and skills cooldowns, but that's, besides the obvious fact that his skill is unusable with non cryo dps.
Yanfei is called budget Klee pretty much everywhere, and being a pyro dps with a dmg output comparable to a 5* is definitely something worth mentioning. While they clearly won't make another busted character like Bennett, I feel like they hit the right balance with these two and while I understand that Sayu isn't that good, being another healer is always a plus since there's so few of them. I really hope Sara will be on par in the right comp, love her design.
