Most people objecting about balance usually have no clue and shouldn't be listened to. Heck, half the people here would claim the game is already balanced and anything new would upset the balance. In my opinion there is only one thing to pay attention to, and that is if something is used.When discussing job adjustments, an important aspect to keep into account is balance between all jobs. That's why it's important that everyone has a say in the adjustments of each job- whether they play that job or not.
Do people use defender? If yes, then it is fine, if no, then it needs an update. Repeat for pretty much all abilities and spells and you have your answer for what is balanced and what isn't. Exceptions are of course tiered things. If you got a stone I and a stone V you can't really claim stone I should beat stone V for balance reasons.
If SE only listened to people's complaints about things being unused, then they'd know exactly what to work on.