Tactics for Rampart.

Dwarves and Ents are very slow.

For this, you need to position your hero to gain momentum each turn.

Pegasi are fast and hinder magic, but they are quickly destroyed.

Try attacking with them with a delay. (It will be even better if you also apply a mass slow effect to the enemy)

Then I add unicorns and GOLDEN dragons.

Judging by the golden dragons, I wonder how much game time you spend playing a single map...

It is also unclear why many suggest covering up the elves.

...and they are helpless in melee combat.

Elves should SHOOT, not fight in melee. When they are covered by other stacks, they will naturally last longer and kill more.

Most cities have monsters with an area-of-effect attack (dragons, phoenixes, liches, magogs, etc.), and if they don't, there are corresponding spells (meteor shower, etc.).

The whole point is that it may not even come to "meteor shower, etc.", the game will end sooner. As an option, use two-hex units and preferably have a tactic. In general, with Rampart, you have to play either against Castle or against Dungeon. (Black dragons are rare in Dungeon).