A good bard will play their first mage's ballad at the 50%-75% MP mark to get the healer back to being topped off, depending on the content and if there are DPS checks.

In this way, you top the healer off, then while the healers are topped off, they are regaining mana.

Of course, this isn't to say that if you know your healers will be fine, you can't just play Foe Requiem or a TP song, depending on what you're doing. Bard is a situational class.

but most are too full of their own DPS to do anything.