Hi there,
Also having the same issue here.Geotiffs are loading in ArcMap properly but not in FME.If you use the CoordinateSystemSetter it will force the image to the coordinate system but the origin will still be 0,0.
If it's a GeoTiff the georeferencing is stored in the file's header.FME should be able to read that, what do you see if you use a GeoTiff reader and then direct it to an Inspector?