The most difficult alternative

In duels, with weekly increases in damage, the Hive wins against everyone except the Chaos Domain.

What kind of battles are these?

Yes, it can be done that way, but the configuration should only be as follows: Mages - Nagas - Titans.
Thanks to Illusions, Djinns can create a powerful stack out of nothing, and with Phantoms, a mage hero is virtually invincible!
By the way, it is beneficial to take Cockatrices. They will be useful even in small numbers.
In addition, the Song of Peace is useful for a caste that only needs one Djinn.

In the final battle, Djinns are not as useful as Nagas. Any illusion is removed by dispelling or canceling spells, and it makes little sense to take single units when you have 5 heroes; all that remains is to hit with lightning and cast a general slow/joy spell. But this seems pale compared to the triple attacks from teleportation.

I like the ability to remove half of the enemy's army from the battle. For the Terror caste, only one Nightmare is needed.
It's scary when a single Nightmare disables a large slot of Angels or Phoenixes!

It lasts for only three rounds. Also, there is a penalty to speed and a limitation in slots, so either there will be no powerful stack or there will be an additional hero. Or do you run around with two heroes?

A stable is needed in any case. The Order of Paladins is very useful at the start. The Abbey - morale has never bothered anyone.
And if you take Crusaders, then on the second level you will have to take Ballistas. Otherwise, the incredibly strong Arbalests will remain the only ranged unit.

Ballistas are the slowest unit in the game. Their speed is 14! Why are they even needed?
Besides, they require more wood than Pikemen. With such costs, there is a risk of not being able to build cavalry in time.
In general, no one plays with level 1, 2, and sometimes even 3 in online games. Especially not in Fortress Battles.
And the strength of Arbalests is not that great, and morale can be raised by a Tactician if necessary. In general, morale is not very important when clearing neutral creatures, unless there is antimorale. And then, morale can be increased through tactics and artifacts.