Any spriest, lock, UHDK, boomkin, or even ele via CL will destroy your pet with pretty minimal effort. Healers dont' always have the gcd's or mana to keep a pet topped off so you can sac pact when needed. You sac pact on anything but a full HP pet and you may as well not even use the talent (or take the 20% HP from gosac/link). Great for duels or bg "swifty" vids but dont' see it holding up in practice. Especially if lock teams actually happen more than 1:50 games.

I could see running a pet w' gosac and soul link and just kill it after you silence or whatnot when it got low. Risk is having the pet gibbed while you are CC'd but its a possible strat for having an extra interrupt or dispel.