First person, for the most part, does not work well in an MMORPG because you can't see yourself. MMOs are social games and full of epeen. You want to show off your latest gear and accomplishment to other people. In Skyrim, you don't give a shit what you look like because, in the end, there is no one else to look at you. This is also the reason why there is a character portrait in your UI. A lot of people like to see themselves and be reminded.
I agree that a far-zoomed out third person perspective can help shrink the world and take you out of it. The best compromise is an over the shoulder, closer look like Defiance or Gears of War.