See, the thing is is that Tranquil Heart does basically nothing on a Red Mage, since we literally cannot gain hate even if we tried. Like I said, all it is is an insult, a spit to the face, of an already long-since dead aspect of the Red Mage job.

I admonish the person who earlier claimed that this was slightly above Shield Mastery, because even that has a situational use or two for the reduced spell interruption while soloing (and I was offended by that, anyway, since I like soloing on /PLD).