It works against being killed completely, unless you are right on top of it( which if well placed, or in the right spot guarding a camper, it will be). It probably does work better. It just leaves you one shot from death.
Not to you, but everyone who thinks this is a whine thread: I don't run sit rep or blast shield, as they do not bug me enough to. I would rather run other perks that fit my style better. If I was whining the answer would be run either of those. I am not. Please don't turn this post that direction. Just thoughts, constructive opinions.