Now, for Bears, this isn't a huge deal. Since the tanking rotation is pretty small and simple, I don't see this changing much. What it does do that's really nice is allow us to not have to fret about Mangle dropping if one fails to land.
For Cats...wow. Keeping the Mangle debuff up is one of the most complicated parts of our rotation. You always, always, always want to make sure your target has a Mangle debuff before you apply either Rip or Rake. And Mangle is not a particularly low-energy cost ability.
Previously you could maybe get by using this every other rotation. It depends on how much you're critting. Now you'll be able to go an average of 8-10 rotations between every Mangle. That's more Shreds, and that's huge.
I'll probably wait for the people over on EJ to do the number crunching for me and then just pass it on to you. But yeah...wow. That's going to be a big boost. I may have to do a PTR copy tonight and do some comparisons to post tomorrow. I'm all giddy at the thought, though.
Additionally, this change could free up talent points spent in Improved Mangle, as we'll be using it much less frequently. Similarly, you may choose to spend fewer in Ferocity as well, although Rake will still be big in our rotations, so maybe not.
Beyond just us, though, Rogues and Warriors should be very excited about this change as well, as Bleeds are a decent part of their damage rotations. Now when we're stuck in high-mobility fights there's less of a chance that the Mangle debuff will drop off the target, which means more damage for them. Everybody likes big numbers!