The PhD (Dphil) in English has much to be said for it. It's good training in scholarly method. It instructs the student how to handle large projects. Occasionally (too occasionally) it adds to the store of human knowledge. The downside is that it pre-specialises the mind. It encourages a scholar, in their early twenties, to draw the boundaries too tight. This, in turn, leads to the greatest bane of current academic life: field specialism.John Sutherland was writing about English professors, but I think his thoughts could be broadly applied to the historical profession. In history, I don't think that field specialism per se is bad, only that so many specialize in a field so early. The traditional PhD track encourages people to travel from undergrad->PhD without ever leaving the Ivy covered walls for, on average (I guess), 8-10 years of professional development.
"Can you teach Wordsworth this semester?" you ask. "No," is the reply, "I'm a Keatsian. Try Snodgrass. He did his PhD on the Prelude".
Every field, be it engineering or history, encourages specialization, but the academic environment offers an opportunity to conduct deeper, more thorough and more general investigation into the broader field of history than do the professions that require entrance into the "real world" of capitalist society. However, the reality is that the traditional PhD track encourages a rapid narrowing of focus from the general, to the specialty to the near-microscopic examination of a particular area. The result is often akin to studying a blade of grass in one small patch of one corner of a vast field. One acquires a deep and thorough knowledge of the particular blade of grass and the soil from which it grows. As a matter of course, knowledge of the wider patch in which the blade of grass is located is also pretty thorough, but as the area expands--from the patch, to the corner to the field--knowledge becomes shallower. Would it be better to require that young historians be more general in scholarship? That instead of embarking on a deep-sea voyage for the "Golden Monograph" right off, they should test the coastal waters in dugout? Would a young historian be better served by being encouraged to research and write for publication shorter pieces-- at first, more general pieces to be followed by topically narrower pieces--as a way to practice before taking the monographic plunge?
As a non-traditional grad student, I realize that I don't have all of the insight necessary to answer these questions. I also realize that my particular situation--an older grad student with a non-history undergrad background--may bias me against the traditional uninterrupted PhD track that culminates in a dissertation, which hopefully gets published. With all that being said, how uninformed am I? Does specialization occur too soon?