I know this is an old thread, but I'm having the same issue on a Samsung T699; I've read and re-read all the suggestions here and still don't know how to fix it.
My phone was ok and suddenly the "Phone" app started eating up all the battery. I uninstalled recently installed apps (although they didn't seem to use much battery, according to the Battery indicator provided by Android) and the problem continued. I now have the same apps I had when the phone was working smoothly, so I suspect the culprit are not new (and uninstalled) apps but the old ones I've been using that may have got a faulty update.
I installed Greenify, but since my phone is not rooted there's not much it can do (and, boy Samsung does add a lot of useless apps by default!).
I also installed GSam Battery Monitor to check what happened.
The weird thing is: the problem suddenly stopped. I don't remember doing anything other than installing those two but well, I was happy. But it only lasted for 3, 4 days (and 2 or 3 full battery charges). Then it came back after I hadn't used my phone more than a few second to send a few whatsapp messages.
I usually have bluetooth and GPS off, and only keep wifi and mobile data on. And the phone worked ok for 2 years with this configuration.
This is what the Phone app did today in the 30 minutes the phone was not being used right after I plugged it off from the charger:
I force stopped each one of the included packages (the ones that let me do it, since others just don't allow force stop) and it kinda seems to have solved the problem, although I suspect that now the whole phone functionality won't work.
Any hints on what might be going on, or what I can do to find what's actually draining the battery? Thanks.