The Art Director

I guess you could call the art director the supervisor for the art team. He/She is expected to stretch the capabilities of the team to ensure a high quality outcome and to set standards. The Art Director will probably rarely create a piece of art on paper, but in their head, and explaining the ideas with the team, who then expand it further.
Other Responsibilities include working with the recruitment team to ensure that the art team is the best they can get, mentor less experienced artists and delivering constructive feedback on the ideas produced. Aswell as being an exceptional artist, you also need to have very strong communication skills. You will constantly be giving feedback and advice, aswell as being able to problem solve and make effective decisions.
As for myself, i would rather be an artist, rather than the director or manager, as you get to produce more artwork/models, which is what i enjoy. Also due to the face that my verbal communication skills aren't brilliant to be honest, mainly due to lack of self confidence.