Is growl supposed to be causing so much aggro? I'm only level 28, but even since level 10 my pet has been able to growl a target and even if it isn't attacking that target, it's usually enough aggro for my pet to hold that mob for 5 or so seconds while I kill it before it even switches to me. I've only leveled a hunter one other time on a different server but I remember having to be careful about DPSing a mob even if my pet was attacking / growling it so I didn't pull aggro. But maybe growl wasn't working as intended there?