As long as you do know that guarding the healer in that fight is probably the best choice since no way jose a dps will be able to rip from you after using that many taunts on the boss after the freeze.
I would hardly describe "one" as "that many". He drops aggro after each freeze and a dps can pull aggro once the dogs are dead but that's just a case of bad tanking then.
As for guard on the healer - just don't do it. You're not helping anyone.