This question is mainly to healers as they get to see the health bars of the tanks more often, but other people can chime in as well as tanks are more than just a damage soaking sponge, they also have unique utility that can increase the quality of life of many encounters (Warriors/Monks have movement, Pallies have the "Hand of" buffs, DKs have more varying defensive CDs, Druids have... uh... sssstuff, etc)