I agree that the Defender path feels odd, especially since you only get a few abilities that let you defend for others. Otherwise the Defender just makes himself really tough and get ignored while not doing a whole lot himself. Even worse are the additional defense when defending traits, they only get used when not able to attack, like when you are moving to the enemy. How about passive auras that benefit units that stay near the hero? Or some type of vengeance mechanic that works like Revenge, but for when other units are hit, so not hitting the tank makes the tank stronger.