Each Dwarven kingdom by itself could make war with any other nation in the setting and have a good chance of winning. All three kingdoms by themselves are a superpower unto themselves.
- The Three Dwarven Kingdoms were not wrecked during any war. Still have their populations intact (whereas most Horde races are small tribes of hunter gatherers, and most other Alliance races are refugees of ruined kingdoms).
- Can build automatons, and the Dark Iron dwarves can employ fire elementals, further bolstering their numbers with strong and expendable forces.
- The Dwarven make use of tanks and machineguns that would rip most other militaries and fortresses to shreds. The physical strength of an Orc or a Tauren counts for nothing when they have grapefruit sized holes in their chest.
- Has airship technology that enables rapid deployment and withdraw. Can also conduct bombing campaigns.
- Wildhammer Dwarves breed griffins to ride, again allows for fast attacks that few can defend against.
The only race that really has the Dwarves beat are the Draenei with their spaceships, shield generators, and death star lasers.
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Draenei and Worgen are physically stronger. Draenei are also far more advanced than the Dwarves. Gnomes also invented nuclear technology and teleporters.
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Don't need sea ships when you have airships that go faster, can fly over land, can fly high enough to be out of reach of the enemy, have machineguns that shoot down anyone who does try to approach, and can drop bombs on anything below.
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IIRC Draenei are physically stronger but Worgen are definitely more agile.
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Druids were always a Night Elf exclusive class. Making them available to the Tauren and the Trolls didn't really make sense, IMO. Nor does it make sense for Dwarves to know them. Besides, Dwarves already have plenty of unique stuff, like their engineering, their runesmiths, their Griffin riders, etc.