After about 20 attempts at Gorespine (who’s located in the Dread Wastes on the lower west coast), I finally stumbled on a combo of standard Level 25 pets that worked:
1. Alpine Foxling Kit
2. Emerald Turtle
3. Arctic Hare
The strategy that worked for me was: Dazzling Dance, Howl and Bite from the Foxling Kit, then Headbutt, Emerald Bite, Healing Wave, Emerald Bite from the Emerald Turtle. Finally Burrow, Dodge and Scratch from the Arctic Hare finished him off.
Hope that helps!