In a gacha game, a character's power output is generally proportional to how much you've invested into them. My main damage dealer (Chenxing) in this case, has 4/5 of her Manifestation traits active, and her signature weapon is at Tier 2; which is the highest you can obtain for a 5* weapon. But in all honesty, you don't need to have this level of investment to get this kind of a clear time for this boss. Chenxing and her signature weapon (no manifestations), can obtain competitive times for this particular boss because her two support characters (Fenny and Enya in this case), just have very powerful support abilities. A friend of mine got Chenxing and her weapon during her last rerun, and his clears are roughly 5s slower for this boss, which is pretty impressive. As such, that's more of a testament to how powerful the support characters are if a newly obtained character who has been out for a while, is clearing very quickly. So in reality, the support characters are actually doing all the heavy lifting in this case. Hopefully that helps.