Military academy or RTS club.

they are called Vespid, or simply, flies
but this works not only against the Undead; they are a real pain for everyone.

Of course, not just against the Undead. Against them, harassment is key, and the main goal isn't necessarily to take over their base to start building; the struggle should primarily take place there.

at least the buildings help the Orcs somewhat

But their buildings are destroyed much faster)))

Warhammer has completely ruined me; I've even abandoned StarCraft, although I play it well. After that, Warhammer feels incredibly unfamiliar, and I'm not playing it as well as I'd like to))))

P.S. Other users pretend that they only play Heroes day after day xD

Why? Many people are genuinely satisfied with Heroes. I'm just too lazy to upload my game list; in the Games menu, I have 27 games, and that's just the ones I play frequently))))) I should upload it)))

P.S.
Once the face is shown, people will follow))))) I mean, write in a simpler way; I understand, but I doubt anyone else does))))
P.S. P.S.
I'm not really in the mood to think right now. I'm currently learning about the Imperials, mainly to understand how they will counter me)))))

Added 1 minute ago
I'll write more in the evening when I have some ideas)))