Hmm, when I created my char, 2 months ago, I couldn't get pitch black hair. It always turned out greyish or blueish or brownish.
I don't know what patch-level it was at the time. If I have time I'll retry to create a character with ravenhair. Maybe that was fixed then.
Just a tip for this. If you go the Grey Black, then in the 2nd hair color option their is a black option max that to 100%. That's how I get pure black hair. It still looks red black when you have blood in it tho.