It's not really a characterization issue. The races being hiveminds with some exceptions is a given. The Forsaken actually have a decently robust cast, especially compared to how dire the tauren are with having only Baine and Hamuul or the Darkspear having Rokhan and Gadrin, it's just that they don't see much use. That and Blizzard are lazy. Rather than making Belmont, Faranell or Lydon Warfront commanders, we have Sira whining to us about how life is pain. Why? It's not because they don't remember them, they're there. It's because if Sira is a zombie, then they can mirror the boss fight with Maiev.
The real issue is much more basic and much easier to solve by people who can't write for shit. Personal power. There are no Forsaken other than Sylvanas who have a chance against Tyrande or Malf. Tyrande didn't need even more of a power boost. So they either need to buff some up or, what would have been better, have it be something like Maiev vs Nathanos, since they're closer to the same power level. Or you know, the best option, which was to have Tyrande kill Nathanos and have him later raised at the cost of a Val'kyr. It gives the Alliance a win, has the same end result, since the two bints can be raised earlier on and it allows Sylvanas a modicum of depth by giving some of her lifeline away to save her boytoy.