I have a question, or rather a thought that can be easily formed into a question, that gives me a lot of trouble when I'm thinking about classes. Could a person who's generous, selfless, caring, or otherwise outwardly helpful to others be an active class? Could, say, a Mage use their knowledge to lead the team and guide them, even though that's generally a job attributed to a Seer?

Of course they can, but it’s like being Introverted- Sure, you can hang out with others and enjoy your time, but ultimately you need some alone time to recharge. Being ‘selfish’ doesn’t mean you never do anything for others, more than it means that you need to take care about yourself to be happy before you can properly help others.