You can even create an army of 7 mummies by using only 1 mummy per unit.
I think that in this case, "fight to the last" won't help; you need at least 2 mummies in each unit for this ability to work.
As for Armageddon, the AI only uses it when it's cornered – when it doesn't see an enemy or when the enemy's forces significantly outnumber its own. This situation arose at the end of the game, and instead of "speeding up," the AI could have quite reasonably used Armageddon. Before that, it didn't use it for good reason.
