Xaldavan, a Blizzard posted on the European In-Game Customer Support Forum, posted yesterday about a change in the casting priority of hunter pet skills:
There is an issue where ‘damage dealing’ pet abilities have inconsistent casting priority over Growl, and we will have it resolved in a future content update to avoid any future confusion or problems. I am sorry for the inconvenience caused by this.
I scanned the US forums but don’t see anything similar posted there. Still, this means that someone somewhere knows what’s up and is working on a fix!
My thanks to Bratty for bringing this to my attention.