Say wha? Mystic found that threat is clearly scaling with Pet AP, and not with Ranged AP (he shot RAP way high using the Core of Ar'kelos and a few other gear pieces, and had no noticeable affect on threat generated by Growl).
So not so fast on that Growl change -- if it is going to be implemented in 2.4.2, it hasn't been put out there yet (which, considering that the 2.4.2 testing is supposed to be almost over, makes us think it won't happen this patch at all). Of course, if the fix doesn't come out, then the original problem is still there. These Growl issues are turning out to be a huge headache for both Hunters and Blizzard.