It's useful to toss out when you're at low MP and have some kind of MP recovery ability ready, since the damage is high and you only need 280 minimum MP i believe, or at least the help says it costs 280 MP. I haven't been too low on MP with Regen around

Aside from that, it's essentially your emergency escape. You can't recover MP while you're being attacked and since your MP is low already this gives you a means to get out of that situation.