- Pets should not be able to CC bosses.
By "CC" I mean "Crowd Control", a term that refers to stuns, freezes, knockdowns, silences-- major status effects that normally cannot affect bosses (through player actions).
The abuse of cycling through certain pets (eremes, executer undead, inverse) will lead the majority of current and future raid bosses into revolving around the same pet strategy. If everyone in a raid has eremes the fight can be more or less avoided completely through constant stuns. Especially with the new pet cooldowns it won't take much coordination to throw a bunch of stun pets at the boss; each raid member alternates throwing one out every 10-15 seconds and you can kill the boss while he's infinitely unable to fight back.
CC pets also lead to problems with bosses. Stunning Eremes himself can affect when/if he even summons the tornado (once I had two tornados on me, another time I had none)-- and stunning some bosses like Ratmaster can really glitch him out where his AoE's become completely unreadable and he himself becomes visually bugged so that melees find it impossible to hit him.