OK, this is annoying... now that I've tested it again to put the displays as Extended -after playing around with different drivers- it seems there's no more problem in Extended mode. It doesn't matter whether I use the TV or Monitor as primary.
Cloning the display brings back the screen tearing immediately. By the way, you don't need to stream Netflix over a slow connection. You get the tearing with basically anything: mediaplayers, games, youtube, even scrolling down a long document can cause it.
My problem is, extended displays are great when you have a multiple monitor setup. If you have 2 screens that are in a different room, where you can't see both, you really don't want to be extending your screen. It's a huge annoyance to be working on a display you can't see so I would really love a solution for cloned displays.