It seem's like software because if you have awake status on phone all the time those battery drain graph is normal. But mostly software issue will be solved if you restart or reset the phone.
below is my battery graph http://i66.tinypic.com/20gijh4.jpg
Wifi will not take battery that much, some apps or process is always awake on your phone and this make your phone doesn't get into sleep mode.
There is an apps in the playstore that can trace which apps does awake your phone but unfortunately it need a root access.
You can find or googling about wakelock detector without root, some people find a way with ADB command but I never try it before.