They were OK, even very good a year ago. In that time sts released many legendary pets with massive stats and some of them (like blinky) great passive attacks and aa. Several arcane pets with even better happiness bonuses, pa and aa were released as well. They are quite affordable atm. For some mysterious reason though sts decided not to bring mythic pets on par with the rest. Lemon and lime is actually worse than slag and grimm. The latest addition is very mediocre as well. Considering there prices and what a person can get for that much, no one should use them. They are only collectables now imho.