Finally! I had to uninstall FF because it was taking ~5% per hour, so in a 8h night, 40% of the battery was eaten by FF, even if I killed it there was a process somewhere
If I'm reading this patch note correctly, they didn't actually fix it using too much battery, it seems they fixed android over reporting the battery used?
I've been using Mull for a long time and had no issues. Recently installed Iceraven, phone got quite hot already after minutes of using it, battery drained fast. Not sure that is this but it sounds like.