I think that you answered your own question by saying you needed to use a D-Light Vixen plug-in to run the D-light unit.
If you could run the D-light via the DMX plug-in or whatever, then your LE-to-LOR cable might work.
However, I think the D-light uses a different protocol (language) than DMX, and so in order to use both, you'd need two dongles - one to talk DMX, and one to talk D-light.
You might asking the question of if the D-light controller understands DMX on the D-light forum. I know both the guys that started d-Light and they should be able to answer your question.