Xingqiu (行秋) is a Hydro support character and friend of Chongyun. XQiu lost his job and got replaced by Yelan. XQiu is a midget with a feminine appearance.
Xingqiu is mainly used for his off-field Hydro application and sub-dps through his burst. The burst lasts 15s and has an 80 energy cost. At C2 it is extended for 3s, making the duration 18s. The C2 will also decrease hydro res by 15%.
Constellation Lv. 6 increases the damage of every third sword rain attack during this Talent's duration (creates 5 sword rains). Xingqiu regenerates 3 Energy when the third Rain Sword attack hits enemies. Normally, sword rain alternates between firing 2 swords and 3 swords. With C6, the order is 2 swords → 3 swords → 5 swords. There is usually a 1s delay between successive waves.
Without any Constellations, this skill at Talent Level 10 has a scaling of 97.7% per sword. On average, there are 25 instances of Rain Sword DMG, resulting in a total scaling of 2442.5%. At C6, this skill at Talent Level 13 has a scaling of 115% per sword. On average, there are \(10*5 = 50\) instances of Rain Sword DMG, resulting in a total scaling of 5750%.
We assume Xingqiu has a Hydro DMG Bonus goblet. He gets 20% Hydro DMG through his passive. The total DMG Bonus on the burst is $$46.6 + 20 = 66.6$$ However, Xingqiu's burst does not snapshot. This is the key difference between XQ and Xiangling. In practice, most of the time XQ is actually off-field, so most of his burst will not be able to receive Bennett's ATK buff. By contrast Xiangling can snapshot Bennett's buff and retain the ATK boost for the duration of her pyronado, even if she is off-field. As computed in other places, Bennett's buff can increase damage by around 1.5 times. So we divide XQ's dps by 1.5.
The burst has a 20 second cd, so the DPS at C0 is $$x_0 = 1.666*2442.5/(20*1.5) = 135.64$$ This is underwhelming. It's true that Yelan with her HP scaling is unaffected by Bennett's buff, but it's not like Xingqiu benefits much from Bennett either since XQ is off-field most of the time and XQ's burst does not snapshot. By contrast Yelan's HP scaling already builds in Bennett's ATK buff, making her more versatile and deal more damage at C0.
Now C4 gives 50% more damage to the E during the Q, and this is a multiplicative increase (times 1.5). Other types of multiplicative buffs include Yoimiya's E skill.
The DPS at C6 is then $$x_6 = 1.666*5750/(20*1.5) = 319.3$$ Note this is really all single target damage. Other characters will have a greater advantage in AoE situations.
Suppose that Xingqiu uses 4p emblem and 200% ER for 50% more dmg bonus. Then $$x_0 = 2.166*2442.5/(20*1.5) = 176.35$$ and $$x_6 = 2.166*50*115/(20*1.5) = 415.15$$ This is less than c0 yelan. Sadge.
Childe and Xingqiu are sometimes compared. A C0 Childe can do more damage than a C0 Xingqiu. At C6, Xingqiu may be competitive in single target damage with a C0 Childe. However, Childe has better AoE, has Riptide, and his Hydro application does not cost energy whereas Xingqiu's Hydro application does.
During the early Mongol/Yuan empire, a Jin dynasty Daoist scholar named Qiu Chuji, also called Master Changchun, disciple of Wang Chongyang, met Genghis Khan in Central Asia and discussed Daoism with him. Perhaps this anecdote serves as some inspiration for the 'Xing Yun' relationship between Chongyun and Xingqiu.