Personally I'd rather "clean up" the hunter class, and add a consistent concept to it. At the moment it's kind of a mixture between what you'll see as rogues and hunters on other games - which is a mess.
Keep in mind that it'd not just adding a new class that's work. You need abilities and skills - and new ones as you level up - and not just today, but also in a year, and two years, you constantly have to add new abilities for each extra class. Same for loot: when adding bosses, I'd not just have to add loot for four classes, but five - and not just for the current bosses, but also retrospectively for all previous bosses, and all future bosses. It does get out of hand - and especially if there's a class still "being tested", it makes sense to fine-tune that class.
As for skins - you can do that already, to some extend. Like, there's nothing stopping you from changing the ear shape in the sprite sheet, other than that you need to stay within the "confines" of each individual limb (you can make it smaller, but not bigger, because the client takes a rectangular region that's pretty much exactly as big as the graphic - partly for memory reasons, and partly to keep the sprite sheet graphic small).
