- Combat: "I solve problems by facing it directly, with physical might."
- Support: "I solve problems indirectly, with natural talents."
- Magic: "I solve problems with unnatural powers."
There's a binary split between solving problems naturally (Combat/Support) and unnaturally (Magic.) Then, there's another binary split between natural direct methods (Combat) and natural indirect methods (Support.) There doesn't seem to be much point in splitting Magic that way, since many spells are ambiguous and can change based on interpretation: "I zap him with a lightning bolt" sounds direct, but "I ask the spirits to zap him with a lightning bolt" sounds indirect, despite having an identical outcome.
To those three roles, we can add a fourth pseudo-role, Hybrid, which is "I solve problem in a combination of ways". That's where I put the Cleric. The Turn Undead mechanic, which I'm so fond of re-purposing, becomes just a particular way to implement a magical (Command Spirit) or natural (Gather Followers) ability.
Things like "I solve problems with illusions" then become either mechanically distinct subclasses or non-mechanical role-playing choices. Either way is possible. Each specific class is thus an answer to one of these questions:
- What kind of direct action are you good at?
- What natural talents do you have?
- How do your unnatural powers work?