Quote Originally Posted by Packetdancer View Post
Because the scaling is determined at the time of the FATE spawning in; it's not going to be able to easily adjust the mob health pools and such on-the-fly once the mob is already instanciated, especially if combat's already underway when the number of participants present increases (or decreases).
IIRC HP adjusting on the fly has been a thing for at least world bosses in WoW since like MoP I think. Obviously they are different games but it's clearly not something impossible.