I don't know about the other ferals flay, but I've played feral and gotten glad pre-insta clone, as feral (and) resto in multiple brackets, and as other classes so I really try to not overreact.
I think Cat summed it up pretty well, but it's not as simple as our healer dispelling (for feral) like it is for a lot of melee.
We have to shred (1) and there is a range bug with our bodies (2) that makes it insanely difficult to stay on people when you're snared at all, much less rooted/powershifting. There is a fair amount of time if I'm chasing someone with proper running skills I can white hit them, but I cannot use special abilities at all, much less shred.
<3 sohfite for explaining part of what I was talking about.
There is alot more to it though.
Did you know that our kick cannot be used while rooted, because it tries to work like a charge?
Did you know that feral survivability is and has been centered around the ability to spam shift/jump and gtfo since, well, forever?
We can only instant cast when we have used a finisher. To use a finisher, we need combo points. To get combo points, we need to hit our target with special attacks. Being unable to use a global to shift in/out of a root is going to reduce our combo point generation DRAMATICALLY, and it is already rather low when compared to rogues.
I could keep going on forever about what this change would do to feral, as this is a massive nerf to the core feral ability to stay mobile.