Like I said, "Even the USN haven't come up with one [a solution] yet", all they have is an idea. A pretty sci fi idea at the moment.
Assuming the "a" element of MaRV isn't a dedicated countermeasure and that your Df21 isn't a million miles off a No-Dong, then while not perfect, I suspect the cousins are a little further along the road than you suggest.
http://www.mda.mil/global/documents/pdf/aegis_tests.pdf