Looks more like the regulator has died as you say.
If you are comfotable and have both the skills and equipment you could change it out (50/50 chance)
There is a common theme over the last 8 months or so to indicate an issue with above 10 volts killing real arduinos. You can find a lot of posts about 12 volts or higher killing a board.
Clones seem a lot better in this regard.