Tactics for playing as the Dwarves.

The following help against dragon lairs: Erls/Jarls with regeneration and light magic; a high-level Ingvar with a large number of warriors (there will be losses, but they are usually worth it, especially if there is teleport or Surprise Attack, which significantly reduces losses); a high-level Karl with light magic (take Storm, Blessing, and 2 levels of ranged attackers; Battle to the Last is also helpful); any high-level hero with dragons, a few warriors, light magic, and preferably luck (dragons don't deal much damage).
All of these methods can be used starting from week 4. All of these methods have been tested in practice.

P.S. It is highly recommended to give Ingvar and Karl the Battle Fury skill.