The only fight I feel like bard as support is even a worthy mention is final boss ... Turn 5 Twintania but even then the more gear you get and the faster the fight goes there will be no need for bard songs. I mean I say no need for them but I do ballad every now and then for like 30secs for battle voice. The game is not designed around any of the content needing any certain job other then ya need a tank and healer all DD jobs can be used in every fight and be successful. With that being said the answer is no there is no content that a support brd can make or break the encounter.