I think the function in the Wi-Fi setting had bug. It didn't work for me.
U should use tasker to sleep ur Wi-Fi every screen off. That's what I'm doing.
Sent from my Nexus 5 using Tapatalk
Google Nexus 5 32GB White
stock ROM + Franco r33 kernel
dalvik+bionic library optimization
disable fast dormancy
KRT01B Radio (Radio 4.4.2 suck)