there is not enough evilness to research everything. there is not even enough evilness to research half. maybe there is enough evilness to research a quarter of all technology. that is after destroying all hero buildings and the creature that provides 750 evilness. mana generaion, even after it is fully researched is too slow. naga is too weak. they got one hit killed by a manaeater(its actual name is likely too offensive for this forum). room capacity is too low. that is compared to dungeons 2 and it is mor expensive too. they really should improve the balance.

Are you writing about the campaign? Because in the skirmish, the good beings reappear strengthened, and the hero's buildings are rebuilt. Evilness was never a problem; eventually, you can produce any resource infinitely.