I think some of you are missing the point here, allow me to try and explain:

Say for example MRD at R30 unlocks DRK as a Job. Now DRK as a Job comes with attack bonus, reduced defence and an increase in magic potency for dark magic. It also has it's own skills like Bloodweapon and Souleater. Now I can take my DRK job and place it on the class MRD but what Cairdeas is trying to say is that the Job should not be restricted to just MRD.

I agree with this I do not want DRK to be restricted to using a G. Axe, there would be no harm in allowing you to equip a sword (GLA) and then placing the DRK job on top of it to create a sword wielding DRK. Or when new classes get implemented like G. Sword or War Scythe I should be able to level those up as you do now but place my DRK Job on top of it.