Magician %/s (KMS FLY 2 & GMS Dawnveil)

Kikyou Kekkai's duration and cooldown are the same. If you use cooltime reduce, you would recast it every 180s. If you use persist, you can recast it every 200 seconds.

that might be true but that would only work on stationary bosses, on bosses that you have to keep moving is better to have multiples out to have more consistent damage output, and on bosses like CHT that have multiple platforms if you cast it and then kill that part, you would have to wait the cooldown to recast it on the next part and so on.