I have been suffering some really bizarre WiFi issues on my rMBP since upgrading to 10.10. I'll suddenly get latencies of a second or more. Switching WiFi networks or even turning WiFi off and back on again will solve the problem for a short period of time.
I just tested this fix to do sudo ifconfig awdl0 down and my ping times are consistently low.
I just tested this fix to do sudo ifconfig awdl0 down and my ping times are consistently low.