There are many forms it could take, let's look at some. We'll even start with the absolute closest possible to Divine Hymn, just to make you happy
1)The bard gets 4-5 song spells, each is channeled for a long duration, say 30 seconds. And can continue to attack or heal, move, and use their other spells during the song. Perhaps particularly strong abilities end the song and put a brief cooldown on it.
Song of Healing: Heals a single injured target within 40 yards every 2 seconds
Song of the Wind: Increases the movement and attack/casting speed of a nearby Ally by 5%, switching every 4 seconds.
Song of Burden: Slows enemy attack speed within 40 yards by 10%
Song of Blades: Lightly damages all enemies within 40 yards every second.