My response is biased as I work here and all so take what I say with a grain of salt :)

While a class DLC may look like a money grab on the surface, you have to take into consideration the amount of testing for balance and bugs that goes into these kind of things. Not only do you have to test for balance and functionality but you also have to make sure that a particular class has its own flavor and doesn't feel like a reskin of another already established class.

Please note that I have no insider knowledge into how Kerberos goes about developing a class for the game but from reading their forums I think they take balance and fun quite seriously :)

If there's ever a GOTY version of the game made, we'll be glad to have it :)