Update: Since posting this, @Ikralla replied to say that he has noticed the changes in live.
WatchDev posted on Twitter this little tidbit about pet tanking.
@FenixAU Many raid bosses are flagged to do triple damage when meleeing player pets. We really don’t want pets tanking raid bosses.
— Watcher (@WatcherDev) July 29, 2014
This revelation came about because a player noticed his pet taking a lot of damage on Staghelm in Firelands. I don’t know if that was in live or on the beta. If it was live then this exists now, otherwise it’s a planned change for Warlords.
Some players have expressed concerns on the impact of older content. Depending on how old that content is it may not be an issue. Once we’re in Warlords gear, I suspect that anything Wrath and below won’t require any tanking to solo.
Even Cataclysm raids will be a lot easier. Perhaps a heroic could pose a challenge. The real test will be with Warlords content and Mists content. So far Hunters are taking this in stride.
— Solarflair (@the_solarflair) July 30, 2014
So why the change? Blame Warlocks!
If this is not in live now, then events like the all Hunter raids could be harder to pull off in Warlords. If this is live then it means that tanking a current tier boss with a pet will be much, much harder.
At the very least you want to really make sure growl is turned off when you raid.
So there you go, pets as real tanks not intended. Thoughts? Concerns? Go!