I removed my App Killer, have screen on full brightness and have regular use of NESoid, SNESoid, Mobile Data, Wi-Fi and my battery lasts a day to day and a half dependent on how intensive I use it even if listening to my music/audio books and I leave them running while I fall asleep at night.
First of all ensure that your data sync schedules for your apps are around every hour or two and not every 2 minutes.
Secondly all I'd recommend is that after removing your app killer go through each app opening them and then using your back key to return to the home screen. Then use Android System Info app to check its CPU usage. If the usage is 0 when its a background app then don't worry about it. If it is using CPU in the background remove it. Alternatively go to settings and applications followed by running applications. Whatever is still running there that isn't a native app again remove it.
Anything running after returning to home screen and even worse using CPU power has been coded badly.