Not to excuse autodesk, but to offer a band-aid: in autocad, text2mtext will convert dtext into mtext. It's an expresstool command, which means expresstools needs to be installed seprately. On the bright side, it comes free on the AutoCAD disc (and has for a few releases now.)
if you cant fix it on the export end, at least there's a quick fix once in autocad. 🙂
Dan