Meh... What are the stretch goal classes? Ranger, Bard, Monk, and Druid? IMO all 'unnecessary' classes, and actually make sense as stretch goals. Put dev time into the meat & potatoes classes and add flavour if/when you get more money.
Bards should never have existed. Their abilities could have been rolled into other classes (magician, paladin) to strengthen them, rather than creating a 'jack of all trades' class. Same story with Druids, whose only real defining ability was snare. Rangers? What makes them a necessary class? A bow? Couldn't the assassin class just have a skill tree for bow combat and tracking? Unnecessary flavour class - get it the fuck out in the interests of streamlining development. Speaking of unnecessary flavour classes... Monk. Unless FD splitting is in, the only reason for a monk (unless it's an avoidance based tank) is so people can see cool karate moves.