As for idiots who won't revive you I have two comments. 1: I'm sick of using my cloaking, or active camo, to sneak into the middle of an Atlas and two turrets only to have you revive yourslef with first aid when I make it to you.
and 2, which is more serious: In any real-life basic first aid class, one of the first things they'll teach you is to survey the scene first as there could be dangers that will make you, the rescuer another victim. This can apply to ME3 multiplayer. Sometimes, its just the wiser decision to try and clear the area before reviving a downed teammate, or leave him there hoping you can make it in time.