I believe the approval process is more a case of meeting some development point and finishing paperwork than Microsoft actually deciding to allow the game or not.
With D2:ED and DKS it was the publishers who dealt with Microsoft for the Xbox version, while for DC Larian is funding the development themselves. The approval process may be slower with Microsoft dealing with a developer rather than a publisher, or Larian may not be in a big rush to do all the paperwork when the game is relatively far from completion.
