Which faction poses the greatest challenge for the Dwarves?

No matter how many times I've played as Dwarves, I've never won. I've lost to everyone while playing as them. Their attack is the weakest of all factions. They can still win with their defense and hit points, but the chances are slim. The Dwarves have the biggest problems with mage units. In the Duels for Helmar, Erin won only once, but it was a real struggle!