Question about fast casting

[jamesmackswell]

Do higher levels in fast casting only affect the skill named Fast Casting, or is there also a passive effect that doesn't require Fast Casting to be cast?

[Efflixi]

The higher you raise it the faster you cast skills. That simple.

[Gwyndion]

The higher you raise it the faster you cast skills. That simple.

I put 8 levels in fast casting, and i'm thinking about removing them and putting them in inspiration/domination since i'm a demonation/inspiratio/illusion mesmer, mainly domination