Pig type (snaggletooth, wrathjaw) pets rarity is "common" instead of "legendary". Since this rarity does not exist on pets - lowest is rare - but you will see the "common" subtitle as soon as you open the egg, that causes an extreme low damage output on the regular attack of the pet.

It is an ancient season 2 bug which was never fixed despite the numerous bug reports on it, I guess the latest jahooty and barney fixes were more urgent.