Well one thing the MCH Job storyline mentions during the first quest is that it hints the WoL has a head start over other MCH. For example, A Limsa starting WoL would be mentioned to be a Limsa adventurer implying he or she already have some skills above other people with a Gun. So most likely compared to other characters the WoL is the only ones that start out as lvl 30 while the NPC start out as level 1.
