Yea, no one wants to haul around more gear then needed. Also, I understand stage real estate can be a premium at times.
I am inclined to believe it is more of a software thing then a driver thing. Since you switched compatibility on the program sides of things (compatibility mode doesn't effect drivers) and the fact that only channels 1-4 are effected and not the whole dongle as a whole farther adds to this assumption. If it was a driver, all 512 channels would not work/act erratic/cut in and out. Now could the Nuendo driver be effecting the MyDMX software, completely possible. But I don't think it is the MyDMX driver itself.