So - you are assuming that space science is solely NASA then? While that make up a large chunk of the resources for space science, they are not the only resource. As you say, DoD does provide instruments such as DMSP and LANL as does NOAA. In Canada our resources are small and we often have to use multiple agencies just to cover over a small project (for example, our current project uses funding from NSERC as well as CSA and CFI grants.
NASA does have several multi-spacecraft projects (see THEMIS for example). But, you are correct, ESA does have a leg up on this sort of stuff.
Now, don't get me wrong. I think that human space flight does have it's place. My question at this point is more "Is it worth (scientifically) putting money into human space flight or instrumentation and robotic exploration and space technology and engineer?" I would say without any reservation, that human space flight, at this point, is not worth it. Is it worth sending a couple of men to the moon to collect a few rocks and find out some tiny info about the 50 square km that they land in or use a high resolution imager to map the moon? Then using that same technology - adapt it to map Mars? Or Europa or Titan? That spacecraft could also have instrumentation to study high energy particles near the moon, looking at safety issues for long term stays - all sort of useful science that would lose out.
What about developing the engineering and technological means to allow for long stays on the moon? Spend 5-10 years researching astronaut safety, building materials, biospheres, ecological and environmental surveys for using natural resources - then go to the moon for extended stays of weeks and months? Using this technology to then go to Mars? It is the choice of where to put the limited funds for the next 5 years, 10 years... where will it be of the most use?