My vote goes to actors too. It's embarrassing how much extra work they require compared to wc3, while providing little real advantage. Sure, there's a lot of cool stuff you can do with actors. It isn't worth the added complexity or development time in my opinion, though.
Runner up prize goes to weapons, which I think have no real purpose. Weapon attributes could've happily just been made part of the units tab, since some weapon effects are inherent to unit animations anyway (like backswing and damage point), and I can't think of a single reason why weapons have their own tab.