The Overmind, yes.
The second is the second hero I would like to see in the game, some form of a Giant, since pretty much each game has a version of it. Basically serves to be a massive moving wall.
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If you include Angel skins, we actually have them all. Tyrael, Malthael, Auriel, Angelic Diablo (Diabael?), and Angelic Valla (Valliel?)