I feel like we get this a lot on Tonberry Novice Network. 'What should I play and why?'

Answer is simple: There is no answer at this stage. Previously it would have been 'Not PLD!' for tank, or 'not WHM!' for heals. Which was when you are competing at endgame. None of that matters anymore. And -NO ONE- knows how 60-70 will go. Ask the bandwagon bards. All jobs are useful in all fights now.

Go for what feels right to you, and what brings you the most enjoyment. While there always exists a meta, a good party will find a way to compensate and turn use it to their weird advantage.