I’m watching the first Iron Man and noticed the gunner in the Humvee is sticking up into the air waist deep. He has a Ma Deuce, not a Gatling gun. Looks like a sitting duck. It would seem a ring of armor could wrap around and at least provide rear and side protection. I guess there might be better protected versions and this one was chosen for the film.
Was the Humvee itself armored? Because a foot or two of armor won’t help you much if the only thing protecting your lower torso and legs is sheet metal and glass.
They do make several up armored variants, including ones with a shield all around: Continuous Army innovation yields improved gunner protection | Article | The United States Army
And some variants replace the gunner with a remote controlled turret: https://ndia.dtic.mil/wp-content/uploads/2010/armament/ThursdayReunionJosephScheneck.pdf
I don’t know how common those are though.
PS see also the successor and partial replacement, Joint Light Tactical Vehicle - Wikipedia