Just because one of those nations lists a certain specialty doesn't mean they're the only ones who produce that good.  Take Somervale for example; it'd be absurd to think that they're the only nation that produces weaponry and has formally trained soldiers, but when you hear that those things were attained from Somervale, then you know it is likely going to be very high quality.  Additionally, there are bards colleges in most major cities in all five nations.  It is just widely regarded that Swai is the most dedicated to arts and education.  As such, your characters don't need to come from a particular nation just because of their class.