The attached piccy shows my testing routine.
There seems to be a bug in the Autodesk.AutoCAD.Interop.Import()
comDoc.Import(fn, (object)ptArray, insScale);
If I insert at 100,200,0 with a scale of 1 the dxf comes in at 0,0,0 at 1:1
If I insert at 100,200,0 with a scale of 2 the dxf comes in at -100,-200,0 at 2:1
If I insert at 100,200,0 with a scale of 3 the dxf comes in at -200,-400,0 at 3:1
I'm sure you see the progression
I'll do some more testing and report it to the ADN.