Dark Knight Astrologian and Machinist are all 2 years old at this point, so most people dont consider them new. The new classes are Red Mage and Samurai. When they announced the jump(boost) potions they specified that for awhile they would be restricted. You wouldnt be able to jump multiple jobs, and you wouldnt be able to jump the new jobs. Around patch 4.1 they were going to re-assess and see if they still needed the restrictions. So for now, you gotta level up Red Mage(or samurai) the hard way.