I think you have a better view on the bigger picture, but I would say when you take the whole manpower of the Army you are not taking in the support aspect of the Army that are not necassarily boots on the ground. Marine Corps god bless them have most of their support taken care of by the Navy. Navy corpsmen attached to Marine units not Marine Medics is a great example of this. This is why the Marine Corps has a higher percentage of "boots on the ground" than the Army does. Only recently has the Army begun to streamline. An example of this is recently the Army discontinued their book-binding MOS. They are doing this by using civilian contractors more and more. However the Army is a much bigger organization than the Marine Corps and that means a huge amount of support assets that go along with it. That takes up numbers.

As for IED's I have been in a few Strykers when they "Blew up" and they seem to do fine as far as survivability. If they would except the associated risk and allow sniper teams to set up along main MSRs where IED's are a problem I think that would be more effective. We need to stop IED's from being planted not sweep through them after the fact.