The idea behind this change is that magic in this world is not too uncommon. Pretty much every chief of the Vallheim, for example, has at least a couple of ranks in some casting class. If someone works outdoors a lot, or is a hunter, farmer, wilderness guide, etc, they probably have a level or two of Green Mage. An architect or guard might have a couple levels in Black Mage, as would a battlefield commander. The idea is that magic is pervasive but limited in its power, hence only high-level pure Mages getting decent damaging spells.