I use foe only in a party with two casters during dps races like P3 in T4 or Titan's heart phase, usually until I'm down to 800 MP myself, then I stop it to save mana for healers if they are in need.
It's the easiest and probably the only really responsible task for a bard to pay attention to the party's MP. Is the healer still above 2k? Is the tank struggling to keep enmity with low MP? I usually battle voice my first ballad, then stop it after those 30 secs to focus on damage dealing again.
And I disagree with bards being the ones always standing in AoE. That's simply not true. We are the only ranged job who can deal damage while moving, not like casters or dpsing healers. I fail to understand any bard who can't get out of AoE (latency being another thing here).