Reworks are necessary, else it's just adding ever more and more buttons. Eventually you just can't add any more buttons, some jobs are already at the reasonable limit. Ast comes to mind as a job that really just has too many buttons. Ninja too - I don't know how anyone can play some of these jobs on controller. I have an mmo mouse and still fill up at least three full bars with ctrl\alt\shift modifiers because there are just too many skills with so many being situational.

So, they have to. And sometimes that does mean that there are going to be some big changes to how jobs play sometimes.

It probably doesn't help that many of the jobs are amalgamations of jobs from earlier games - like AST for example having FFXI Corsair abilities, but it's a healer, and a DPS. Would be nice if SE would just get a clear vision for what they want some of these jobs to be.