During the work on Oblivion, they actively experimented with mechanics and content.
Former Bethesda VP of PR and Marketing Pete Hines recently spoke with dbltap and shared his memories of working. In particular, he spoke about the creation of The Elder Scrolls 4 Oblivion.
He recalled Todd Howard's philosophy - the creator said that "great games are played, not created."
Pete Hines explained this philosophy: "that is, your every idea of what is good and what is not matters only when someone starts playing - that's what determines whether you succeeded or not."
In search of a good solution, Howard iterated the combat system, and marketers tried to find reliable advertising material:
"In Oblivion, the combat system was changed three times during development. Therefore, we tried not to talk about how the combat system works [in advertising], because we didn't even know if we had the final version. Therefore, we tried to bet on those parts of the game that we thought would resonate with people."