It's not difficult to think of ways a bard could work in WoW. The game is full of mobs that attack with sound magic, with the most high-profile recent example being Imperial Vizier Zor'lok. There is a sound elemental lord, Murmur, so the idea that sound magic doesn't fit in the lore just doesn't hold water. On top of that, Hearthsinger Forresten, a rare boss in Stratholme, is a literal bard, and uses shouts and songs along with a bow to debuff, cc and attack. In other words, this is a real class lore-wise, we just can't play it, same as demon hunters, necromancers and all the rest.
As far as the taboo against support classes go, it's a relic of a time when there was no such thing as dual spec, and the cost of changing specs was prohibitive. Neither of these is the case anymore. The class could easily accommodate a dps, healing and support spec.
With that said, they would probably put in another class or two before they did this one.