No Darkspawn, so no Thedas-style blights. I mean, we've definitely had epidemics and pandemics of deadly diseases, which share some properties. And wars, and sometimes one at the same time as the other. But humans fighting humans, and diseases that kill you but don't make you come back to fight for the other side.

As for your first question ... historically, all three of those, but right now mostly they control the means of extracting the natural resources necessary to power the machines. And they've got enough money and influence as a result to do a lot to block alternatives before they can get off the ground. Influencing political leaders, acquiring and crushing smaller enterprises, that kind of thing.