If implemented right, job specific traits should only provide a slight boost to the job and not be a complete game changer. Given how XIV's formulas work, it would probably be barely noticeable. Say for example, the use of "insert said action here" would have certain percentage chance of procing that job trait. Many classes/jobs already work like that.

To be honest though, it depends on the person behind that job build. A drg with dragon killer could still be outclassed by someone on any of the other dps classes if the person playing that drg is bad and/or not performing well. The same goes for any other job.