Defensive, considering the specifics of this map and the heroes and their stats. Orcs have fewer towns, but a very strong hero.

Um... I don't quite understand... strong in what way?
The Orc has a total of 13 stats, while the Elf has 14, and the Knight has 13. So they are equal.
Is it the specialization? +1 to attack for each stack killed every 6 levels? So at level 24, it will be +4 attack if a stack is killed. Is this an overpowered specialization?
Perhaps Kurak has better artifacts at the start, but that doesn't compensate for the 2 extra towns. 2 extra towns = 4 gold mines at the start + a 4-fold increase in low-level units (like archers). With that many archers, the Orc will simply be shot down.