The point about Zane is well taken. Of course, he could just hear Ruin---he wasn't being tele-operated like the Steel Inquisitors seem to be. If the spike went through (or near) his spine, maybe it gave Ruin some--but not all--access to his nervous system, which with proper control might be enough to make him hear a voice.
This is still just a simple hypothesis, but I don't think Zane necessarily proves it wrong; it just needs refining.
As for the objections to electricity---first of all, Ookla has a point. The Mistborn world seems to work just like ours, including such things as a spherical world, Newtonian orbital mechanics, and radiation hazards from the sun, things which most people considered totally irrelevant for the first two books. Thus it is simplest to assume that electricity does exist, just like in our world, unless proven otherwise. The fact that the people in Mistborn don't know how to use electricity to make themselves and their lives better proves absolutely nothing; that was our worlds situation for most of history. Ruin, on the other hand, should know about electricity, if it exists, but it would hardly be inclined to tell us how to use it properly.