Disclaimer: This is not a nerf <insert faction here> post. I simply want to hear about all factions experiences using grenades and having them used against you. I primarily play LSM and use grenades often to try and clear a point or as a last ditch effort against melee. With that said I cannot recall a time when a grenade has dropped someone at 100% health/armor. I've dropped plenty of grenades just before I died to melee and they are only ever stunned unless I was able to put a quite a few rounds into them previously. I have died a number of times from grenades when at 100% health/armor and it is usually when I get stuck on something in the environment and cannot get turned around fast enough. With orks being the heartiest of all factions I don't think it would ever be possible to 1 shot them at full health/armor with a nade (I am fine with that). It also seems that CSM are just tough enough to survive when at full health/armor (not sure what that leaves them with, but it can't be a lot). In theory it should be possible to 100% an Eldar player although they always seem to just end up stunned as well. In most cases I think they are moving to fast to take any considerable amount of damage. Again, this is all perception and I would like to hear more from other players and factions.
I think it is due to the overly long warning indicator that lets people move an ample distance from the nade long before it goes off. Usually only people sprinting into a location with bad luck are the only ones to eat a nade full on.
ignore frag grenades if you want to kill the enemy. use krak grenades instead. also remember to shoot the grenade to make it explode where you want it.
It is also long stun which allows to finish off any opponent that you can shoot at. Making frag grenades be primarily stun\harassment weapons was one of the best decisions across the alpha, IMO.