the hand grenades seem to not deal appropriate damage if they are in extremely close proximity to a character, e.i. standing directly on top of a grenade, laying prone on top of a grenade, or laying prone with a grenade inches from your face all do not kill.
i can understand not being instantly killed by frag from a few feet or meters, but being able to lay on top of one or wear it like a pair of sunglasses and being able to walk away is absurd.
throw a grenade at your feet, stand on it, lay on it, give it a kiss, pick your poison, you'll walk away with no more than a scrape.
Grenades are really, really weak. By comparison, any other explosive is liable to kill you even if you have a sturdy structure between you and the blast.
Hand grenades and 40mm grenades are both ridiculously easy to survive.
It's problem with explosives (mines at least) in general, tens of tickets about the same issue can be found with search.
I have noticed this too and am finding grenades quite useless and annoying to.
i must say though that i have found it to be more random then consistent, i mean one time i through a grenade within two feet of an enemy and he didn't die but then a similar occurrence happened and the enemy was killed.