There is just no reason to ever be a Pugilist, Marauder, Gladiator, Conjurer, Thurmaturge, Archer, Lancer, post level 30. No matter how you slice it - they're inferior to their counterparts in every way.

What if: At level 30, you get a pair of quests, one that unlocks your "Advanced Job" (Ninja, White Mage, Black Mage, Bard, Paladin, Warrior, Etc) and another quest that unlocks the ability to assign a "Sub Job" to your "Basic Job."

To wit: If you have a Soulstone equipped, nothing changes. However, if you do NOT have a soulstone equipped, and you've completed the associated quest for that job, you can then equip a "Sub Job" to it.

Example:

Lv. 30THM vs. 30 BLM
STR: 35 < 40
DEX: 93 < 98
VIT: 110 < 115
INT: 138 < 148
MND: 87 < 92
PIE: 118 < 123

Wearing the EXACT SAME GEAR - Black Mage is superior to THM in every way.

With Conjurer as a sub, you have an additional 12 Mind and access to spells like "Fluid Aura" and "Repose."