Terrible news for boar owners! In all the investigation over pet aggro in Patch 2.4, it was determined that the great extra-aggro effect of boar’s Charge ability followed by a Growl is a bug and will be removed in a future patch.
Here is Hortus on the WoW Bug report forum:
I have confirmed with the developers that Boar’s growl ability getting such a large bonus to attack power based on charge is a bug. Growl should only benefit from the hunter’s attack power and get no benefit from buffs to the pet’s attack power.
Expect this to be changed in a future patch. If you disagree with this change please post about it in the suggestions or class forums.
Note that the thread Hortus posted in is locked, but I do believe we should follow his suggestion and post our thoughts on this in the Suggestions and Hunter forms.
Potential silver lining: perhaps fixing this bug will help prompt them to look at threat generation across all pet families.
 Incidentally, you can find a list of 2.4 Known Issues on the WoW Bug Report forum as well.