If you had been following the forum for the last month, the producer had said along with the emmity increase, they would be adding x 2 more damage increase to players then before, so basiclly everyone will have to relly on true tanks again for content level 51+.
I think they feel realistically that your pet is a one time shot at killing something and should not provide unlimited tanking/solo'ing on mobs above the strength of your pet.
Sorry this happend, but it was comming sooner or later.
Might want to run to the Auction house and stack up on complete VIT gear, there was something about VIT affecting it greatly.