The Secret World manages to buck this trend, using the same core Dreamworld Engine as Funcom's Age of Conan. A recent interview with lead programmer Øystein Eftevaag discusses the way that the engine interacts with the newer game, how the unified engine helps both games, and what special features the game is using in a technical sense.
Eftevaag explains that the Dreamworld Engine benefits chiefly from cross-pollination; improvements made in terms of optimization for Age of Conan can be imported to the engine on The Secret World with minimal extra legwork. The engine also uses a series of dynamic equations to determine what player characters should be able to see, subsequently leaving obscured areas blank to save on processor cycles. It's an interesting look under the hood at the technical side of Funcom's upcoming conspiracy and horror title, even if this particular dream world is tilted toward a nightmare.