A Vampire growth unit defeats a Black Dragon. A Black Dragon defeats a Djinn growth unit. A Djinn growth unit defeats a Vampire growth unit. If only the tactics are well thought out. And the enemy's morale won't unexpectedly drop.
If you remove the "ineffective" Vampires and Bone Dragons with their retaliatory attacks, what's the point of attacking Crusaders? With "effective" Skeletons and Imps?
Справочник по НоММ-4 http://handbookhmm.ru/pamyatka-dlya-heroes-iv.html
Памятка по НоММ-3 http://handbookhmm.ru/pamyatka-dlya-homm-iii.html
и HotA http://handbookhmm.ru/vyishla-obnovlennaya-pamyatka-dlya-homm-iii-hota.html