Oh what the fuck, I just read Zhou Yu's passives.
So the reason why I've been able to melt bosses and get fast clears with him was because he literally has a 30 percent passive damage buff against bosses.
I think I'll be using him as my first traversal 6 character.

Is there a recommended cumulative level progression for each traversal level? Like, if I want to tackle traversal 2, what is my recommended cumulative level? 100? 150?