There is no criteria… Its just my subjective evaluation… My sensations when I use those heroes… when I meet those for enemies… or use them in Constellation maze, or watch video clips made by others… thats all of criteria. And there is no SSS support because of their limitations… in many cases they die before using rage skills… so only buff or debuffs r working… and in most cases standing one more dealer is much better than wasting one position for supporters… Besides, several tankers have healing + buff skills too. They get aggro from enemies.. heal, revive, deal decent dmg… survive for quite long time in battle, use rage skills several times. So I evaluate tanks little bit higher than others.