UNIT - Creature Balance + Visual Changes

If we take the practical criterion of "what is most advantageous to put in harm's way during an attack" (based on which Titans were suddenly classified as tanks), then the best "tanks" are level 1 units, and even better are level 2 units with high defense. They are, admittedly, disposable, but they can withstand attacks of any size (with almost no losses). These are the ideal tanking units (according to that criterion). So, perhaps we shouldn't use the term "tank" for a unit with low survivability, like the Titan?