This is not a user error!
Brand new build: ASRock Z270 Mobo, DDR4 Corsair 3300 Mhz, Samsung 850 Pro SSD, GTX 1070 FTW GPU, 1300 Watt platinum Corsair PSU, Core i7 7700K CPU. No overlays, no third party software of any kind. Changing all the settings others have mentioned; clean installs etc etc etc. I can play for hours but eventually I'll get this same error.
It has nothing to do with NVidia or AMD as it happens across the board. PC components are not the factor either and Windows has had NO major updates since patch 3.55b. This is strictly an SE issue and needs to be addressed by same ASAP.
http://i.imgur.com/k0hoG1J.png
EDIT: the above added screenshot was all of 5 mins ago and I was standing idle in The Mist. It's 5 AM no one is online so it's certainly not an issue with population.