I'd be surprised if this happens to a full sized adult. Similar to a cackle of Hyenas attacking a lone lion cub IMHO - profoundly cowardly behaviour from a gang. A single Orca would get smashed to pieces by an adult GWS if it struck 1st & managed to take a chunk out of it's head or whip a fin...
Boats. Helicopters. Other great whites. Orcas when they are alone and not mob handed. South Africans. Yanks. Shark cages. Whales. Junk. Quints.
They eat anything and everything.
#teamshark