i have not done the testing but my buddie fitted with corvette G3 was killed in front of me in less than 20 second by someone using a clipper with frags. basically the clipper got behind him shot his corvette and drop the shields almost instantly, i imagine that the clipper had engineered frags. by the time i notice and was able to turn my ship to my buddy his hull was halfway thru. and once the clipper PK him it just bailed. and i this is usually how frags are used by gankers, they get close to you and out of sights to get real close. basically when i play in open and see a cmdr with frags i kill him asap by ramming and all weapons free.
here is a video of what i usually get to witness and experience against players with frags.
https://www.youtube.com/watch?v=nDDCHuHHaI8
More missing pieces of information....
Firstly, you have no first hand knowledge of this, that is very obvious here.
Secondly, that video shows a stock standard NPC ship, Expert level, I drop these fast too, without even using frags. so I do not know what to say. even when I went full Beams on my Corvette, such ships did not last long.
Thirdly, your "friends" Corvette, what build was that? what shields and modifications was used? what hull and modifications was used? Was there any hull reinforcements fitted and what modification was it on them? Was shield boosters and what was the modifications on these? For all I know, it could have been a trade corvette, with stock hull, and smallest shield, to maximize cargo space and jump range...
And I do not get how someone can sneak up on your friends, and at point blank range can unleash salvo after salvo... you are not telling the entire story here, which is very evident by the lack of details of the circumstances.