http://www.reddit.com/r/ffxiv/commen...nes_mechanics/

If you are in the red zone for the AoE when the cast goes off, you will take damage. If you move back into it right after the cast finishes but before the animation does you will not get hit. This applies to a lot of things in this game.

Is it bad design? Yeah I'd say so, but you can adjust to it but only when the servers/ISPs aren't having a throttle war/packet tossing contest.