I'm not disagreeing with you on the battery life concerns, but this isn't really the target usage for Surface Pro, is it? Watching that much Netflix in one go usually means you're at home, so you can run a power cable. No sense in wearing down the battery for no reason beyond a very minor bit of inconvenience.
Netflix was a bad example because it requires a good quality Internet conenction - but running hours lots of DRMed videos in one sitting without a power cord is quite a common thing to want to do, e.g. for sitting on a plane flight.