I have found that the false offset issue occurs when defining Shared Coordinates via 'Aquire Coordinates' when using DWG files stamped with a coordinate system definition. Revit is unable to parse the Geolocation stamp correctly and uses the Easting offset from the meridian and a Northing origin at the equator as is defined within the stamped projection. This results in a corresponding shift in XY of the coordinate system to reflect the origin for the stamped system, and ignoring the location of the XYZ origin in the DWG. Removing the Geolocation in AutoCAD 'simplifies' the DWG for use in Revit and the Aquire Coordinates tool works as expected. The coordinate system name/definition is however 'Unkown'.
It would be great if Revit could correctly parse the Geolocation definition ( or at least the name) and result in a correct Shared Coordinate system which mirrors the XY Origin in the source DWG.