Hmm.

If your tank doesn't have hate established in a tough fight, isn't it appropriate that the mob will go after healers? Let us consider - in games in which you fight a group of enemies, and one of them is constantly healing the other ones, which one do YOU try and kill first?

The healers - no question. I don't see why the mobs should act any differently. It's realistic that way. As a tank I would rather see a setup or situation where it really matters if I know how to do my job or not.