I killed him with 2 pets, Cogblade Raptor as suggested and an Anodized Robo Cub(1-x-1). Use Bite on the Raptor until it dies, then swap in the Cub and use Maul + Bite. Retch should die from that, if not swap in a 3rd pet and finish him off.
Mechanical Scorpid (1-2-1) worked nicely for this, took off about 2/3-3/4 health. Start with Black Claw, spam Barbed Stinger and if you get a poison proc use Puncture Wound. Keep Black Claw up and rinse repeat until death.