I found that the nearby trash battle-pets to where the primary Wildhammer Gryphon Hatchling spawned seemed to have a higher rate of having them as a secondary pet. Found 3 in a row like this. In total it took 8 encounters with Wildhammer Gryphon Hatchlings to get my S/S which I then upgraded to rare for the Xu-Fu encounter in the Celestial Tournament.
1843 pets
I found that the nearby trash battle-pets to where the primary Wildhammer Gryphon Hatchling spawned seemed to have a higher rate of having them as a secondary pet. Found 3 in a row like this. In total it took 8 encounters with Wildhammer Gryphon Hatchlings to get my S/S which I then upgraded to rare for the Xu-Fu encounter in the Celestial Tournament.