This update isn't a nerf to agility classes, it's just a direct nerf to the agility stat.
We're a lot more than just agility stacking creep punching bags and there are so many ways of keeping crit decent enough to cap at 25% in PvE raids while keeping high PM. With U10, the hunters who have maintained a ~11k-12k crit rating will have to adjust for the agility stat change however, reducing somewhat our PM.
I really doubt this update will be as bad as everyone assumes, especially if you're coming from the PvP perspective where we're getting a direct buff from BFP.
Hunters will find a way to raid-cap crit and if you're not already at 37k+ PM and raid buffed crit, you perhaps just aren't as geared as you thought.