with a lot of rays its not the actual venom that kills, its the barb and where it penetrates that determins lethality most of the time. look at steve irwin, if i remember right it wasnt the venom it was the barb piercing his heart.
also the blue ringed octopus is only dangerous as the venom stops the nerve signals firing to the muscles keeping your lungs going. after a period of time victims recover if kept on a ventilator with no anti venom needed at all. most victims die of suffocation rather than the toxic effects of the venom.
and yes i watch too much discovery channel.