Question [Q] Kitkat 4.4.2 battery drain (CM11 M7 on S2)


I can’t say I’m impressed at all with the SGS2 battery life running CM11 M7 (KitKat 4.4.2). Quite often the battery won’t last through the day (luckily I can charge it at work, otherwise it wouldn’t even be bearable as a phone).
My crappy Sony Xperia J (JB) I had for a couple of weeks as a replacement could easily reach the end of the day with 70% charge still left when I plugged it in at night.

Android battery stats always show Android System and Android OS as the main offenders (around 20% - 25% each), above Screen usage, Voice calls, Mobile standby...
BetterBatteryStats tells me the phone is in the Deep Sleep most of the time, but also that it is awake (mostly at 200 MHz) quite a lot of time as well.

Here’s what I have already tried:

Disabled location services
Disabled Google Now
Disabled Google+ Auto-backup
Opt out of interest-based ads
Disabled back up data to Google servers
Disabled “Android Device Manager” as Device Administrator
Uninstalled all updates to Google Play Services
Disabled automatic updates from the Play Store
Disabled Mobile Data Limit
Disabled Automatic Date/Time updating
Uninstalled Lookout Antivirus
Uninstalled Viber
Uninstalled Skype
Rebooting the phone before connecting the charger
Rebooting the phone immediately after disconnecting the charger

I really don’t want to perform a factory reset specially since I have read some other comments by Galaxy S5 and Nexus 5 owners (KitKat 4.4.2) saying it didn’t work…

So what exactly is going on here?