To the OP: I'm getting great battery life from my Nex 5 on stock 4.4.2 and stock kernel - better, in fact, than my Galaxy S4. I would recommend always returning to a completely clean stock build and adjusting in small increments from there; this at least might help you to isolate the problem (or problems).
I'm on 3G most of the time, wifi at home; NFC, GPS and location turned off.
For Facebook I use the Lifehacker tip of deleting the appalling Facebook app and just running a bookmark to the mobile FB website in Chrome. So much better.
One thing that has massively improved my battery life is Lux Auto Brightness - paid version. This thing, when set up correctly, has improved by battery life by at least a third.
Good hunting. I sincerely hope your phone isn't borked.
Nexus 5 (rooted; stock) / SGS4 i9505 (rooted; S4 Google Edition 4.4.2 Final)