No magic missile
My Bard has high DEX and I am using her as sniper (Rapid Shot etc). At the beginning of fight I pause and use first song, then second (and the first one keeps going because of Lingering Song, then third etc...). All songs are in, I click his bow, aim and unpause. When song effects disappear I pause and repeat.
Song effects kicks in as soon as I play song and last because of Lingering song. In most cases fight is over before song effects disappear. In 95-99% of cases two songs are enough.