Although Freya is one of my main characters, except for certain boss battles, I've never used Six Dragons more than couple of times, with very good reason.

Whenever you use Six Dragons, one of three things may happen to your party:
1) Your HP and MP is fully restored.
2) Nothing.
3) Your HP and MP is reduced to one.

It's a waste of MP. I'd prefer Reis' Wind over Six Dragons when it comes to a quick healing fix.