Well, the first question I would ask (and it's not mentioned in the article - what a surprise), is whether the Secretary of Defense traditionally signs sympathy letters. Were they signed by hand in the 1960s? 1970s? 1980s? 1990s? Is Rumsfeld doing what has always been done, or has he changed policy here? Until we know the answer to that question, it's hard to pass any kind of judgement.
I can tell you for sure they were not signed by hand by the Secy of Defense during WW II or Korea and certainly not in the Viet Nam War. They were mostly signed by the CO of the unit in which the casualty served.