I dont know if nerfing dps is necessary. In PvE, a weaker bard means having a weaker group. The issue is not so much that Bard is too strong, its that melees are not really wanted in endgame groups, so they have to change those classes and make them more desirable.
When they change bard, they should focus on aspects that makes it less desirable to have MULTIPLE bards and instead pick other classes for spot 2-4, so probably less stackable skills/songs.