With Dark Simulcron being replaced by rot I decided to see if any pets had Rot and a critter attack that would be strong against their target once it was considered undead. I only found one Willy but it looks pretty good.
Go 1/2/2 and you've got a great combo which makes you a counter pet to any other pet. Rot to make them undead, Eye blast if needed to be faster and Tongue Lash away for good dmg. Follow him up with a cricket and make sure to Rot the turn before you die and the cricket can swarm then skitter for massive dmg.