Metal Gear Rising: Revengeance had suffered from a bug through Steam that would not allow gamers to play the game offline at all. This was not meant to be required to play the game, and was said to be being patched, and now that patch has arrived. JP Kellams, the creative producer at Platinum Games posted to his Twitter account about the new patch.
Online bug should be fixed and you should be able to play offline now with no issues or in the *very* near future. Thanks to @konami!
The online requirement bug was not the only bug that was being reported as there have also been region lock issues and as well as issues with the resolution. Platinum Games says they are considering resolution options for the future, so stay tuned to see if that happens.