Which class is least represented?

[Uteunayr]

http://p1999pop.dmsimard.com/db/Classes

That offers you a breakdown of the distribution of classes, generally. This doesn't say a thing about demand however. Ranger, Paladin are both low, but also are in low demand. Druid and Necromancer are high, but are also in low demand. Wizards are low, but probably going to be more in high demand come Velious.