Nice list. I do heavily agree on putting Dir en Grey on the list. They're my favourites. And of course X Japan is a must have on a list of Japanese music.
For anyone who wants some more, try Maximum the Hormone. Or go for BACK-ON with the song Chain. They're Linkin Park's early inspiration and you can immediately hear it.

Seeing other people with a passion for Japanese music is so cool. Especially when it comes to metal.