The courier is a complete pusillanimous individual. The courier gets shot in the head and ends up in a coma for a long time. Any NPC that is shot in the head might actually live and be able to stand and fight back.
Not sure where you get the fact that he was in a comma for a long time, it would have only been a couple days at most, Benny's trail was still hot.
Also, you really have trouble grasping the way video games work and how they are not and should not be like real life.
If you want more realism in combat go play an fps or some stuff.