The effectivity or lack thereof of most grenades
I was doing some testing with a build for grenades. To do this testing I went to the shooting range and use the stand at the far left where you have a group of enemies. For simplicity I left the stand at the default setting of easy. When throwing my grenades I was aiming them in such a way that all the targets standing were within the radius of the grenade and had the red lines linking them to the aim point of the grenade.
Even after throwing all seven concussion grenades most of the enemies were still standing. For most of the grenades there wasn't even any floating damage text showing the enemies had taken any damage. In most cases only one or two targets took any damage and once these targets dropped the rest took no damage.
As a matter of fact in one case after destroying all the enemies except for one using my weapon, I was able to throw 4 grenades directly at the base of the target without doing any damage whatsoever.
In my testing the only grenade that reliably and effectively damaged all targets within its radius was the incendiary grenade.