Spotting Cause of Excessive Battery Drain I have a Nexus 6 phone and it has always been amazing with battery power, I can usually go 2-3 days before absolutely needing to charge it and that's with heavy news reading, game playing, phone calls, texting, using the camera, and updating apps. It does all this while having this configuration:


It IS rooted, wouldn't have it any other way.
It has a STOCK Google provided image from Google Developers (currently running LYZ28M)
It is connected to an AC 5.0 ghz Wireless channel.
Bluetooth is OFF by default, use very infrequently to connect to a headphone to listen to things for about 10-30 mins.
All animations are disabled in developer mode.
By default the auto-rotate is disabled.
Location is set to power-save mode (wifi only).
Display lighting is set to auto with ambient enabled.
Camera is to HDR+ (no flash).
Most background services are disabled (except Play Services, UI, etc which are required).
SMS auto-retrieve is off (even though I don't have the original Stagefright issue anymore, can't speak to the Stagefright 2.0)
Power history puts the distributions as follow (no shockers there):


Cell Standby (46%)
Screen (23%)
Android OS (11%)
WiFi (5%)
Google Play Services (4%)
Android System (3%)
Phone Idle (3%)
Voice Calls (1%)



Now that all being said, the set of apps installed on it have always been the same between each re-image that I have done since 5.0 to 5.1.1 now.

However, starting about 1-2 weeks after the latest update, it is draining BADLY, when I said badly I mean within a max of 6 hours (minimum usage) to less than 2 hours (heavy/normal usage) it will drain. To add to the mystery, I have Battery Saver Mode enabled to kick in at 15%, when that happens, if I click on turn off battery saver, it will IMMEDIATELY begin shutting down, which makes NO SENSE, I have turned it off in the past with no issues.

Does anyone have any idea what's going? or can suggest a tool that allows me to snoop with a greater degree of granular control to see what is causing it to actually drain so badly? I have read all the other similar "battery drain" questions and none of them seem to really apply to me (at least I don't think) but resulted in why I included so much detail about the device, so it will save the trouble of having to ask about details of the system.

Much appreciated, thank you in advance.
GSam Battery Monitor is an excellent program that will give you an extremely detailed report of what is using your battery and to what extent. 
However, what I believe this may be is the Mobile Radio Active bug. It is one of the most starred Android bugs in existence. Essentially, when apps that use data are turned on (such as Facebook or Skype), the Android system forgets to turn off the radio until the app that asked for the radio in the first place is force stopped. Google has acclaimed that the issue is fixed in Android M, but I do not believe they have plans to fix it for Lollipop. (I am looking for a source of proof and will edit this when I find it)
In the meantime, Greenify will automate the process of force stopping apps when you don't need them, however, you may stop receiving notifications from these apps.