Yegoriy
I finally finished the map in 163 days on veteran difficulty. The first month of the game was extremely tough, as heroes of a higher level and with larger armies than mine would attack. Luckily, I managed to fend them all off in the castle even without the hero's specialty and without significant losses (I was very lucky to find a unicorn horn artifact near the castle). It's good that the dark elf was passive and never attacked me himself — I think he would have wiped me out even in the castle with his boosted spells. Unfortunately, the Necromancer hero was Zoltan — not only does Vampirism not work, but he also forbade casting Raise Dead, which made it hard to minimize losses.
At first I didn't understand why, after defeating a hero, he would return in two weeks with roughly the same large army as last time. Turns out each computer player has a Teardrop of Asha. 
Also, the witches' coven would periodically break the castle, though I never actually found them until the very end of the game, but they didn't really interfere with the gameplay much, to be honest.
Overall, I liked the map, thanks.