ok look, its quite evident that he made up that lame excuse almost 30 years later, which is when the VD was written. And yes I have seen ROTJ multiple times, and the reason given back then as to why he died was because he came back to the lightside, which is a feat no jedi can handle. Meaning no matter who you are, if you go to the darkside and then come back, you'll die. Granted he had his hand cut off and yea he got shocked from lightning, but thats no why he died. Have you ever had a power surge at home? If so, did the power go off right away, or did it just get weak for a a couple minutes and then go out? Allow me to answer for you, it went out instantly, and so would MECHANICAL Vader if that were the cause of his death.
We have plenty of household electronics that have electricity flowing through thin wires covered with plastic coating.....do they melt? noooooo.
As I mentioned before, the lightning was reserved for the Emperor to show why he was Vaders Master. We thought we had seen everything that could be done through the force, until we see this old ass decrepit man shoot lightning from his hands. Vader could but doesnt need to, and now thats his excuse.
And dooku using it, besides being stupid, is just to show the power of Yoda like someone said before.