The Class Structure is mostly intended for New Lights (In Lore) with most guardians being able to mix the structures. That being said, most guardians will also generally stay within 1 subclass as their primary power, only branching out lightly. So, we have the New Lights. They don’t split or drift away from their respective Subclass. We then have the Average Guardian. They don’t drift too much from their primary subclass. You might see one pull of a Blink on Arc, or some other crap. We then have the upper classes of Guardians. They will actively use different abilities from the other classes employed to best suit them. Like when Felwinter used a Shoulder Charge. They will also make use of multiple subclasses (See Ikora) Then we have The Guardian. In part because The Guardian is the player character, they are one of if not the only Guardian to completely bypass the entire subclass and class system in the first place, able to be a Titan, Hunter, and Warlock all at the same time. Mind you, the Guardian is incredibly powerful, more so than the Drifter (Darkage Lightbearer. Not a Guardian, nor does he follow the class system) so this, plus the fact that we bypass the Class system is a testament to our absolute absurdity. On a tangent, I would like to point out that all the D1 subclasses still exist. Sunsinger and Arcblade both being the ones to no longer exist. They only exist within the lore though. And with Final Shape, it seems as though Sunsingers and Arcblades along with their respective counterparts, Dawnblades and Arcstriders, have slowly been combining into 1 single subclass. With the Advent of both Song of Flame (A Radiance like Super) and Storms Edge (an Arcblade themed super) as proof.