Hustic

Also, for the record, I'm SUPER pale. My artist has always packed in the color, though, so I haven't had this kind of fading on any of my black and grey.

I'm Whitey McWhitebread. When I first met my tattoo artist I think he got a little bit of a tattoo woody looking at all that pale skin. I don't think skin tone has anything to do with why it faded. If anything, very pale skin makes the color stand out even more.
I'd leave it as is, but if you must monkey with it, make sure you get someone really good. They aren't going to "touch it up" they'll likely wind up going over the entire tattoo. If you don't get someone really good you have a better chance of making it look worse than making it look better.

Agreed. He's a good artist but could have done better getting the ink down in there. 

Tattoos fade. That's just how it works. Plus, he didn't really pack in the black. It still looks cool, even if it is a bit undefined now.