On the one hand you have a system where two shots to an extremity will kill you and on the other hand you have a system where no number of shots to a limb, however high, will kill you. Neither one is realistic in terms of immediate life and death, but like everyone is saying in terms of what is being called "combat effectiveness," the former is clearly more realistic.
In Ost it wasen't ment to simulate death, it was there because respawning with a fresh soldier was more fun than lying on the ground helpless for 20 minutes waiting to bleed out.
Combat ineffectiveness is a very real thing, not every soldier who is shot dies instantly, nor is it common for them to shrug off the damage and keep going as if nothing happened (unless it's just a superficial fleshwound of course, and whilst soldiers have been fatally wounded without noticing it, they wheren't fine, they died a few minutes later, and no bandage would have stopped that), walking normally on a broken leg or foot is not really possible, and broken hands and arms would definately prevent you from using a gun.
Things is, this doesen't translate well to a videogame, who want's to spend 20 minutes lying helplessly in a ditch waiting to bleed out? Who wants to keep playing if they can't shoot? who wants to play an FPS game where they can't move? Thouse are the realistic options, that's what would actually happen to you, but does it make for a fun videogame? No, it really doesen't..
This is why Ost just took you out of the action and spawned you with a fresh dude if you got to badly injured to keep fighting, that was the whole idea behind it, and it did work.
The HoS system is just broken though, how do you put a bandaid over a sucking chest-wound and come out of it fit as a fiddle, still able to jump and sprint around? How do you sprint around on a leg that's been shot several times, and where every bone must be broken or shattered? How do you fire a gun with an arm that should just be a bloody stump?
And yet, jumping out of a window that's just 1cm too high will insta kill you..
The Ost system had it's quirks, i woulden't call it perfect, but it did work, both as a videogame mechanic and for the sake of immersion, it was a solid and fair system.
But what we have in HoS does neither, it's just... broken.