My X also seem to drain 5%-7% 8-9 hours overnight, that is not normal? I have nothing running background (I always swipe up to close programs I don't use at the moment).
During use battery goes down about 12% per hour when using Safari to surf internet with display brightness bar around the same level as the sun icon where you do the adjustment. During 30 minute phone call battery dropped about 4%. Does that sound abnormal?
Sometimes battery level goes down faster, like when phone has not been used for a while and you pick it up, it may go down pretty fast 2% and when you keep using it, it can drop another 1% pretty fast and then maybe after 5 minutes stabilize more and then go gradually down 1% every 4-5 minutes of use. That is most noticeable in the morning when I pick up the phone and if battery was like 70% when I first turned the screen on, it would be down 3-4% percent after 5-6 minutes, and then go more gradually downwards every 4-5 minutes.