The real star here is Guoba, the legendary god of the kitchen.
4 piece Emblem, ATK-Pyro DMG-CRIT, Catch
We compute the DPS from a C6 Xiangling with a level 13 Q. We assume Xiangling has a Pyro DMG goblet with Emblem of Severed Fate (for at least \(120(.25)+46.6=76.6%\) DMG Bonus on the Pyronado, which can obviously increase with greater ER). Pyronado has no ICD, so assuming she can vaporize each hit, the damage scaling per hit is:
We assume with C4 (the Pyronado lasts 14 seconds), the Pyronado can hit the enemy around 10 times. The Pyronado has a 20 second cooldown. Assuming we can spam it on cooldown, the DPS is:
So even with vaporize, C6 Xiangling's DPS is less than the DPS of C0 five star characters. Xiangling's main advantage is that her burst is an off field ability that can do modest damage, can snapshot, has decent AoE, and has no ICD.
Note Xiangling's EM can further boost the vaporize damage by a bit. And the above calculation assumes the bare minimum of 120% ER from the 4 piece emblem set. If we assume Xiangling has 200% ER (which is achievable by using things like the Catch), then the DMG Bonus becomes \(200(.25)+46.6 = 96.6% \). The dps is then
For reference the following is the dps without vaporization
If her ER is E then the dmg bonus is \(.25E+46.6\). The dps is: $$x(E) = (1+.25E+.466)*1.5*238*10/20 = 44.625E + 261.681$$ But the max dmg bonus that emblem can give is 75% so the above caps out at 300% (would actually write min(300, E) above in place of E). When ER is 300$ (E=3) then the dps is $$x(300) = 395.556$$
This DPS surpasses a C0 Ganyu's DPS but is still less than Eula, Raiden, and Xiao.
Without vaporization it is $$x(300)/1.5 = 263.704$$ In practice it is very hard for Xiangling to reach 300% ER (200% is more reasonable).
Note her C6 does not buff her own pyronado. Other sources such as weapons and Raiden's q (+24%) can give burst dmg bonus too.