Ogo

Yes, the map is indeed powerful. And it's not just because in 2008, the "Sacred City" scenario became a silver prize winner in the "Best Single-Player" category at the official map contest for Heroes 5, organized by Ubisoft. It's simply fun to play! I agree that the beginning of the map, especially when set to Hero difficulty, is challenging, but as the hero levels up, the gameplay becomes easier and more interesting. Therefore, I express my gratitude to the map's author. I should also try playing other scenarios by this author; there are probably more. 
Also, a huge thank you to the author of the Heroes fan channel, Heroes fan - Remix, for helping with the map walkthrough. This guy posted a walkthrough on YouTube:

https://www.youtube.com/watch?v=BcDmBMXU-zs

His walkthrough experience also helped me. I thought I was playing well, but this guy plays like a god. So, I have something to strive for.