Hmm, so if dfu-util is not working for you… how are you compiling locally and getting that compiled binary onto your Core? Spark CLI?
I know we can get dfu-util working pretty easily for you…
Just drop the EXE from here into a folder like c:/dfu-util/dfu-util.exe and then add this ;c:/dfu-util/ to the end of your PATH Variable Value located in System / Advanced System Settings / Environmental Variables.
You also need the DFU UTIL driver (sounds like you know already but just pointing this out for all following along):