In ff14 its simple, you virtually have no time, as soon as it pops you need to move. Even if you'd technically have a good 1-1.5sec before the aoe animation actually triggers, the game always consider you late.
Weaving is also a good example, if you press awiftcast and a spell right after you start casting the spell. You actually need to wait 0.5sec for the end of the animation. Which somewhat defeats the purpose of emergency cast.