It's not so much that you'd be forced into a mangle spam style of play, it's that you'd be taking points away from other talents which are far generally better for PvP.
With the Bear Form nerf to PI, I would drop that and go:
I don't really see any feral talents here I am giving up. I mean it all comes down to what lvl 80 pvp is like, but if it's gonna end up being similar to 70 pvp then I don't really know what I would change here...
I'm curious about what you think would be a good spec or at least what are some good talents that I'm overlooking.