Eorzea has much Light? How?

[Edax]

So I gather that the problem of the Eorzea now is there's too much Light. The Warrior of Light has been too heroic and the world faces destruction from imbalance.

However, the actions of the Warrior of Light have not been able to stop a World War from waging. Brutal repression, slavery, massive loss of life, endless war and attempted genocide from Warriors of Darkness from another world. This is the world with too much Light? Is the moral of the story that war and genocide are good things that bring the world into balance?

I shudder to think what plunging this into darkness would entail. The Warriors of Darkness tried to wipe out an entire world, mass genocide. How can the story follow in their footsteps? How can we darken the world when nearly everyone dying happened in the "world with too much light"? Am I missing something?