i've found a good combo for leveling a third pet if you are facing the wild pets in pandaria especially in valley of the four winds as pretty much all the pets there are critters or aquatics, use anubisath idol to drop the sandstorm then switch to Anodized Robo Cub for critters and use bite and maul...

http://www.warcraftpets.com/wow-pet-battles/create/9c3/

dog vs bones vs something slimy