I like the above posters suggestion, but coming up with new animations for each buff would be a significant undertaking content-wise. It would also not work for buffs or debuffs that do not have animations, such as the defense down debuffs caused by battle regimens. Instead I would recommend a simple fade graphic analogous to the yellow text that appears over the character model when a buff like Protect is applied. Just have the text pop up gray and fade to black, perhaps gradually becoming hazy as it does so. Along with this, it would be nice if all buffs and debuffs on allies and enemies benefited from this treatment, e.g. when a physical attack -> physical attack battle regimen is performed without misses on an enemy, it would be nice to see "Defense Down" appear over the enemy model, analogous to the current effect with Protect. It should also fade as mentioned before when it wears off. This would keep players informed about the state of status effects without having to concentrate intently on the arrays of icons in the party display, self status display, and target display widgets.

tl;dr simple fade-to-black animation when status effects wear off; expansion of this effect to all buffs/debuffs