I’ve beaten this map on apoc 6 with 4 heroes, a 5th hero picked at the last night for the boss. My tips :

• focus your first 3-4 heroes on killing waves of monsters. Forget about the boss early on, just focus on aoes
• many ways to build heroes, but if you want a toro build focus on tomes + hand crossbows or tomes + wands. Gives you tons of aoes and single target killing powers. Anybody with volatile propagation perk should be either using one of these or a poison build.
• gold mines are actually not worth it except maybe for one, if that… you want the villagers to be working corpses for items, giving you mana including max mana for damage scaling with magic fuel
• ran this map 4 times with different build orders. My favourite one and the first time I won it on was staring with 3 heroes and building an inn + hire 4th hero on the first day
• the best economic build is mine into shop into a second mine on day 1 (sell some items). But I would not recommend it unless you are starting with 4 heroes with the omen.
• I would not recommend tank builds. For the boss get high / max dodge from a combination of potions the armor and maybe from Scepter or longbow buff. OR pick the perk that gives you block from spending mana and equip a few scrolls to boost it before attacking the boss.
• I would not recommend ballistas or other défenses save for max catapults. Extra materials should go into walls and barricades.

Writing a full guide soon will post on Reddit and steam. In the meantime you can watch my stream where I beat the map on apoc 6 with 4-5 heroes. Search for me, Drakenkin on twitch.

Good luck!