Battle Voice is an important skill as well that will make whatever song you're using 2x as strong for 30s. So if you're going to take that hit to DPS for ballad or tp regen, this lets you get the most out of it. I macro'd Battle Voice to say 'Current Bard Song 2x effective next 30s.' and that way the message applies to whichever of the three bard songs I might be using battle voice with. And party members should be able to tell which I'm using- foe requiem puts a debuff on enemy, and ballad/paean have very different looking status indicators. I save battle voice for when I really want it to count- healer is raising another healer and MP restoral needed, or burn phase where I want magic resistance to be -20% for 30 seconds (at no DPS loss to me).

Level 50 Bards who finish dungeon runs or extended battles alongside a party without using their MP for something are typically bad players, but many like that exist. It's especially sad if they have a healer in their party that's able to both heal and use cleric stance to do magic damage, but the bard can't be bothered to cast foe requiem. Using Foe Requiem while solo is usually a bad idea (unless farming lower level enemies you want to pull) but in the context of battle with a party, once a tank has initiated a fight, maintaining/regaining enmity is their responsibility and there's hardly any fight where you shouldn't be able to use foe requiem after the tank's done the initial pull.