For the record, I have seen a pet die from a couple odd mob attacks in beta (an AoE in the Sunken Temple, for example). However, it was very rare, and all I had to do was use the leash or whatever to summon him again right away. There's no raising or such to worry about. These pets are non-entities to the mobs, so they can only kill them accidentally. They can't target them and they won't aggro on them or even notice them.
One day, the Champions of the Fierce Bunny will ride again...<!--sizec--><!--/sizec-->