Try flashing the french EU rom to those having poor battery, heard it's quite decent.
I'm getting stellar battery like on my UK unbranded handset, 7 hours SoT today with 10% left, I'm averaging this for the past week or so actually.
I've tried more ROMs than I can remember right now, over Kitkat/Lollipop/CM, makes no difference whatsoever, always comes out with pretty much exactly the same battery life.