While I understand and even sympathise with the motivations for its creation, I'm not sure that an immensely powerful mega-bureaucracy is the best answer. A certain amount of the politics of fear was in effect here, and essentially the Department was a coordination and combination of several existing agencies.
Having worked in politics and government, I'm well acquainted with the fact that bureaucracies don't willingly give up power and influence, but rather strive to increase it. While protecting the nation is a worthy and essential goal of any administration, a careful auditing of the means undertaken to do so should also be in place. Unfortunately, that latter element doesn't seem to be going on.