listen to this presentation by a programmer from God Of War, its kinda long, but worth hearing. (maybe jump 21 minutes in) part of it covers how they added capabilities for both their players and enemies, and how they tried to make the designers and animators do most of the work. instead of programming alot of unique scenarios, they just made it flexible and data driven.
you can derive from a base class, but dragons and creatures should probably be Pawns rather than Characters, because you probably want more control over their root collision component.