I never manage to get much more than 2 hours on screen battery life. My phone's barely used since I'm at school for like 6 hours, I do keep it on during then though.
I'm using Franco's Kernel 14 as well and I haven't seen any change compared to the stock kernel! Have I got a faulty model or something?
Here's onscreen time:
i. imgur.com/jpXlXHn. png
(Had to use spaces since I'm not allowed to post images yet...)
I've also got the Battery Guru app installed. Still didn't improve once learning mode finished. It can get me through the day but I just wondered why I'm not getting anywhere near as much on screen time even though I'm a pretty light / moderate user