We bought a new Dell XPS15 running 8.1. Been debugging timeout issues on IE. Running the Ping Test option on speedtest.net I'm seeing ping times > 100ms with jitter at 40-50ms (other machines report <25ms with 1ms jitter). Fortunately I have a range of access points to play with and so far narrowed this down to getting "normal" times for us under the following conditions: 2.4GHz G-only access point, 5GHz AC-only access point. Any other combination of A/B/G/N does not work. I've seen a lot of other posts with people trying to get slow connections to work, so thought this might be useful. So right now I'm going to set aside a access point just for this machine and have it configured to 5GHz AC only.
I am sorry you are having problems with the connection using this wireless card but let me help you.
Can you please try disabling the U-APSD? Check below: