http://masteroverwatch.com/leaderboards/pc/us/level
278 is currently the highest, without a doubt he's feeling the effects of playing so much. When I did the HWL grind in WoW I was playing literally all day apart from food breaks and I felt so ill after awhile.
EU has one account at 338 right now, which at 310 hours played is almost 13h every day since release. Looking at their Twitch it seems like it's a shared account though.
http://masteroverwatch.com/leaderboards/pc/eu/level