Your effectiveness is limited, at end game, by the weekly caps on tomestones and gear acquisition from raids. You can "choose" to gear up multiple jobs via these routes, but if you do so you're intentionally making a conscious decision to be less effective than someone who does focuses on a single job.
That was the only real choice (with pros and cons to both options) to be made with regards to stats. Every other job has only one realistic option for almost all situations. It's also likely going to cease being a real choice in 3.2.
