Balance in Heroes 5.

Dwarves are strong, but the balance is definitely good.
There are usually no problems with money, but there are problems with resources – crystals and gems are not abundant. There is also a constant shortage of wood and ore, and sulfur needs to be found somewhere to get dragons.
And the beginning isn't that difficult; I'm playing as Dwarves, and there aren't many problems. People also say that it's easy to start with Ingvar if you immediately upgrade the Mountain Guards.
And the energy rune isn't that rare, especially if you have several castles, but you can also manage without it.
And in general, the rune is a very good thing.
And the creatures have very good abilities, and the skills in the development wheel are among the best.
But even if you take into account all the positive qualities of the dwarves, they don't stand out much among other races.

Added 9 minutes later

And about the Dwarves. They are just too resilient. And with the Tower, it's difficult to take their city on a large map, even for Heaven's Chapaev, and the battle will take place in a well-developed city – this is an undeniable fact. Without the Tower, I agree, they are a normal race; with the Tower, they are terrible cheaters, and it's hard to argue with that.

In my opinion, it's not that difficult for mages to defeat dwarves, even with a VERY large Tower. A large Phoenix more than compensates for all the small dwarves. And with the Sign of the Magician and summoning a swarm of ash trees, you can generally exclude their turn, along with another unit (except for dragons).