Tactics for playing as the Dwarves.

You can hardly deal with Demons. Maybe a hero will fall sooner if they have a sharp mind... Otherwise, there's no chance. Only if you're lucky with artifacts and the ranged attacks hit sooner. In general, a Demon can easily slow down our troops at the beginning and then speed up its own with an aura, and that will be a complete disaster. Whether you like it or not, you'll end up in a defensive position.
And Divine Vengeance simply works wonders with minimal spellcasting. Damage exceeding 1K is quite realistic.

P.S. I don't play on random maps because they turn out to be terrible. On the original maps, you're unlikely to find several identical artifacts. Only if you're looting one utopia after another on some Outlands, but you know that you definitely won't be able to do that against a human player. I only bothered to collect a full dragon set in a game against the computer, but I didn't manage to do it.

Well, I'm just testing it now; I'm playing with a friend, and we're actually playing the opposite – I'm playing as a Demon, and he's playing as a Dwarf, and he's a little better than me, so let's see (especially since we're playing on a map with a mentor, so we'll try all the options). I'm not arguing that Divine Vengeance is an overpowered spell, but you can't really do much with it at the beginning of the battle, and besides, it's not an area-of-effect spell, which is not very convenient... so I'm sticking to my opinion=))...
P.S. You're missing out by not playing on random maps; many maps are actually very interesting, and besides, there's a higher chance that the game can turn in the most unexpected way (which is what I like about them), just the regular maps get too boring over time, and you already know them so well that you can complete them with your eyes closed, and you know all the loopholes and where everything is, IMHO, but that's boring=))