I just started pet battles 3 nights ago. I have a couple of pets at level 16 and 17. I have yet to find a magic based pet. The highest level I have fought yet, is the battle pet tamer quest in Searing Gorge. I think those were level 15ish. I barely won, after losing the first time. So I know I am not ready to move onto the battle in Swamp of Sorrows. And, for that, I read that it is much easier if you have a magic family pet.
So, where do I find those?
BTW, just as an aside, since I can't stand leveling in MoP again, I started the pet battles at 60% into level 88, and am now 25% into level 89, and plan to go to 90 by only doing pet battles. Sure it will take longer, but at least, I hope, I don't have to visit Dread Wastes again to quest to 90.