In my oppinion, a good army it's the base of a good defence.Uppgrade them with all upgrades, and don't worry about there is only King Dain as a hero; Glorfindel and Gloin shall come with reinforcements.
Dwarves aren't the fastest army in the game, but their mines provide the fastest movements of the game. Build several mines across your territories, and put your builders inside the mines. Built a fortress in the battle front, equipied with walls, arrow towers, catapults and the most important, your entire army beind the walls. When the enemies reach the walls, advance with your army trough them. Built statues, wells and mines beind the walls, so that your army can recover after each enemy strike. The mines shall be useful when the nazgul breach erebor by the back. Trough them, send your armies on this last atack to reach victory!
P.S.:Sorry about my english. I wrote this realy fast.
Rammstein2129, the LORDofWAR R, from the tribe LORDS OF WAR.
from Portugal.