The advent of class roles to 4e D&D changed our perception of character classes. All classes now fit into one of four predefined roles within the party: controller, defender, leader and striker. Even though we’ve only had these four roles since the release of 4e last summer, they have become engrained in the discussion of gaming groups.
These four classifications are quickly becoming more than just roles. You could argue that they have become the new default character classes and that the current classes as we know them are just archetypes of the controller, defender, leader and striker. What I’m seeing more often are players deciding to play the striker and select whether they’d like to try the arcane, divine, martial or primal archetype of that class.