I guess no one has a solution for this yet?
The problem is not app specific. The delay in notification happens all across the board. When my phone is sleeping, i dont get any notification. As soon as I wake it up, all notification come at the same time, including Yahoo mail, Gmail, hangout messages, whatsapp, Google voice, twitter and others.
It seems like the wifi/data is disabled when phone is sleeping. I double checked in the Advanced Wifi option that wifi is always on.
Why only few of us are seeing this issue?