How many Warrior of Light exist in story?

[MiniPrinny]

-snip-

This. When you get your first crystal (water), you get to commune with Hydaelyn again, and in that cutscene there are hundreds, if not thousands of Warriors of Light. Every streak of light you see around Hydaelyn in that moment is a Warrior of Light.

What makes the PC different in the MSQ is that they are a Warrior of Light who has accomplished much more than defeating a weak ascian, they have bested trial and primal, one after another. They have overcome cataclysmic enemies.

The Warrior of Light that the MSQ follows is sort of the Elidibus of Hydaelyn's chosen many, the strongest and wisest. But they can't do everything, that's where the others come in, the lesser Warriors of Light do stuff that the PC can't, like take out ascians as needed or protect the people where the politicians fail.

Edit: I should note that me calling the numerous chosen lesser Warriors of Light is conjecture based on the events of 3.4. We saw that just a sole crystal of light was enough to overcome incredible odds and become god-like in power. So if we were to assume that everyone we saw at that moment were those with the Echo who had manifested a crystal of light. Then we as the Warrior of Light are likely far from alone, there just aren't many, if any, who have manifested all six crystals.