At WORST, the druid will be second best at almost everything, and not worse by a wide margin, and best at his own schticks. At best (and 'best' means 'any situation where he has time to prepare'), he'll be better than most at their specialties.
At worst, the bard is third best at something, if not last, second or third best at another, and best at a narrow focus. At best, he's the best within a narrow specialty and second best at everything else.
Also, I find it interesting that many people equate 'the party having time to buff' with 'the DM fails to challenge them.' Your PCs, when tactically astute, rarely if ever have twelve to twenty-four seconds to spare? They never ambush their opponents as opposed to the inverse? Never delay entering a room or charging an encampment to prepare themselves?
As for the fix I favor, I would reduce the druid's spellcasting progression to the bard's. Animal growth then becomes one of the class's capstone spells rather than its "mid-level" buff. Removing the Natural Spell feat would significantly lower the druid's powerlevel, but in a less flavorful way.