I’ve been struggling with poor battery life (read: 10%/hour) last week, and finally I have found a solution. I have picked stock RUU from Softbank, unpacked it, made an upgrade.zip and flashed it. Battery discharge curve became flat and horizontal (using “Juice Plotter”).
Using stock RUU image I’ve tried to flash a few different radio images (32.30.00.28U_4.05.00.11, 32.36.00.28U_4.06.00.02_2, 32.37.00.32U_4.06.00.16_2), but did not see any significant difference, so I decided to use 32.36.00.28U_4.06.00.02_2 for now and maybe investigate this later when I have more time.
Unfortunately stock ROM has some disadvantages, so currently I’m looking into building a joint ROM from one of rooted images, but including some settings I’ve found in local stock RUU. Hopefully this will fix the issue completely, because now I’m getting less than 1% discharge in an hour in standby mode and this is pretty much enough for me.