The auras don't last that long. like 4-5 seconds. The big thing is that you can prime all of your teammates at once before a big fight, whereas other heal-support classes (psycho, drool warrior, red mage) have to tag along with a medibuddy once the fight starts and micromanage more often. Bard's auras scale better as they affect more of your teammates.
If it turns out that both the Red Mage and Bard need a little something extra in terms of offense so they feel more useful, I'll add that later after we get to test it some more.