Yes, it is true that going prone most definately reduces your potential for injury, something I hope holds true in the gameI would agree with you if you are standing up, but if you have dived on the ground there is a lot less of you to be hit by shrapnel although it won't do much with a concussion type explosion and you will likely become a casualty anyway.
Shrapnel is indeed the biggest killer but the vast majority was from artillery, some horrible wounds to be had from 105mm and 150mm shells exploding nearby, I've read accounts of foot long pieces of burning hot shrapnel going through peoples legs who survived it, harsh times.
My point still stands that commonly you won't instantly die from a grenade. Become a casualty sure. I know in the context of HoS a casualty is as good as dead which makes my point a little moot I know.
As an example, when the potato masher was originally introduced the fuse cord protruded from the bottom of the grenade rather than being concealed by a protective cap, this meant that often it would get snagged and explode right against the soldiers body causing terrible wounds often fatal. The point here being that even with a grenade exploding against your skin at your waist soldiers still survived such blasts.
What sort of grenade is being used and in what circumstances is also a factor, a typical potato masher without a fragmentation sleeve being thrown at someone in the open is going to have a small kill radius, indoors it will be far more effective. Alternatively in the open using a defensive frag grenade is a very hazardous business as the potential lethal radius is quite large combined with the huge casualty radius being greater than the distance the grenade can be thrown, making such grenades only suitable for being used when behind solid cover.
The problem with these sorts of gameplay decisions is to get it realistic you have to program individual bits of shrapnel flying about, up close you are bound to be hit but the further away you get the gaps between flying bits of shrapnel get ever bigger. This is all a lot of programming effort though when a simple range calculation=x amount of damage is a hell of a lot simpler. It is with this simplified damage model in mind that I think the lethal range of grenades should be reduced some. It would still be nice to see concussion grenades modeled to be more deadly indoors and a lot less useful in the open whilst the opposite is true of frag grenades which are more useful in the open than indoors where people can get some cover between them and the grenade.
Does anyone remember the predator grenade from the original Aliens vs Predator back in 1998? It actually modeled individual spikes from the grenade giving a proper grenade effect.
Also, I had a similar suggestion once involving the fragmentation properties of grenades, where individual fragments would be modeled with power equal roughly to a pistol round. Sadly, it was the general concensus that this would be a HUGE load on the server side...our vidja game technology is just too primitive at this point... maybe they'll do it for RO3:IS2: