Probably a little late, but don't forget my favorite AutoCAD command "_AECEXPORTTOAUTOCAD". The help file for the 3 main autocad object enablers (Architectural, Mechanical, Civil) explain that this command will strip out ALL proxy information and effectively dumb down the graphics to just graphics that work with plain jain autocad, and create a new file. That file will most likely import into Revit just fine.
jvj