For 3 years, Xinyan was the 4 star with the highest base atk at 249. (Albedo and Morax have 251 atk.) But then Freminet came in 4.0 and Gaming came in 4.4. Damn, the times, they sure are a changin'.

Xinyan scales with DEF. Her E shield scales with her DEF. Whiteblind and Redhorn are good weapons for her. So somehow she synergizes with Gorou, Albedo, Itto teams?

At c2 Xinyan gets 100% cr on her Q (reminiscent of how Bronya gets 100% cr on BA). Her Q does physical damage and is a nuke. So somehow she synergizes with Mika and Eula too.

Besides the Itto and Eula teams mentioned, as she can apply pyro off-field, she can perhaps be used in burgeon teams, similar to Thoma.