Regarding the clouds though,
j2C can get rid of c-cloud early on, jC can dispel a lot, b-cloud is hard to deal with on crossup. A-cloud can be dealt with by either 5C or 3C.
A lot can be stuffed by Zantetsu since it's a wide 2 hit swing, and although you said he's vulnerable on wiff, the goal of most would be to hit the projectile and Arakune at the same time, which means Haku will be avoiding jumps and watching his spacing.
Once he is cursed, he'd avoid unnecessary movement and jumps or close in as fast as possible to get that uncurse hit, sometimes using 623A.