Tactics for complex battles.

Now, a specific situation: a scenario called "Island" (I always forget which one), 1x1, hero difficulty.

Based on the description, it's clearly Contested Island, a normal, almost dueling map.

And the resources will soon run out. So, what do you do next if you can't even build griffins in the first week?

Starting without a tavern and leveling up a hero to level 4 or higher is simply unrealistic.

With a random setup, you get Haven with a hero who specializes in champions.

That's where the whole problem lies. If, by chance, you get a specialist in peasants, a tavern specialist in armored units, no archers in the castle, and only shooters and dryads around, then no clever tactics will help; you're doomed anyway. That's why I don't see the point in playing with random castles, and therefore with random heroes, as there's too much randomness involved. After all, if you started with Vittorio or Dugald, the problem would solve itself. That's why people usually play against each other by choosing a hero and on veteran difficulty.