Should be renamed to Demonic Amplification and it should reduce GCD of all instant casts by 1sec.
The way I see it; reducing GCD of all curses is meaningless when you apply those curses every minute or two. Maybe in a setting where you're applying CoA to multiple mobs but even then your overall damage is probably reduced.
Just trying to see why this is a tier3 talent and doesn't provide nearly the kind of ability the other talents provide.