I'm going to bump this thread back after taking a closer look at Beguiler (Bard's caster counterpart)
Currently Beguiler outclasses Bard in almost every way conceivable.
Beguiler
Mana: 206 - Hitpoints: 836
Piggify: 6 second single target root/silence - 23 Mana - 25 second cooldown
Mass Piggify: 7 second AOE root/silence - 30 Mana - 120 second cooldown
Plaguebomb: 233 AOE damage - 20 Mana - 5 second cooldown
Pulse: 116 AOE damage - 30 Mana - 10 second cooldown
Fireball: 150 damage + Fire
Beguiler's Wisdom last's 3 minutes, effectively giving them permanent increased Mana regeneration. Beguiler also has helpful utilities such as Dispel, Purge, Quantum Leap, and Teleport.
Bard
Mana: 129 - Hitpoints: 836
MelodicBinding: 0.5 second warmup - 3 second AOE slow - 20 Mana, 6 Stamina - 20 second cooldown
BoastfulBellow (I know right): 0.5 second warmup - 80 AOE damage - 20 Mana, 6 Stamina - 10 second cd
Voidsong: 1 second warmup - 89 damage AOE 3 second silence - 20 Mana, 6 Stamina - 20 second cooldown
HealingChorus: 50 HP heal and debuff - 20 Mana - 10 second cooldown
Comparisons for each buffs were listed at the start of the thread (Beguiler still outclassed Bard there). The only place where Bard has and advantage is melee, which is obvious considering it's a rogue spec. Keeping that in mind though to do equivalent damage to 1 PlagueBomb (5 second cd - insta cast) Bard would have to use every AOE it has, taking around 2.5 seconds to cast, and costing 60 mana/18 stamina (Bard would not be able to use these skills again for another 20 seconds). As said before, Beguiler also has far better utility than Bard out of combat with skills such as Teleport and Quantum Leap.
Bard is dominated by Beguiler in nearly every way, yet they are both meant to play a similar role in combat. I believe that Bard should have it's buff durations last as long as a Beguilers to help balance this.