Nightwing *might* be able to work as a solo, or as a *really great* solo, but its noticeable that it hasn't. Ask anyone to name a good Dick Grayson story, you'll get some New Teen Titans answers, Black Mirror, and the Morrison run on "Batman and Robin".
Any title under the name "Nightwing" isn't just missing its "Sinestro Corps War"s and "Batman RIP"s, it's also lacking any decent, memorable above-average arcs. The closest its got recently was when Snyder brought him into the heart of Court Of Owls, but that was still a Batman story!