Just noting that Pharoah has summed it up very well here. the bard is mostly good because its substitution level in Races of Destiny allows you to use Diplomacy as a Calm Emotions effect, trading away the god-awful Countersong and giving you something to do in combat with your pretty self.
A 2nd level bard with a base 16 Cha and those bonuses above would have +19 to Diplomacy, I believe.