Bad reception is going to kill any phone. I recommend airplane mode for where you know the phone isn't doing much.
I seem to be at 20% or so with my 5 by the end of the day, and I don't feel like I use it a lot. When I do, I need to charge during the day. This is subjective, so I won't go into details. Suffice it to say that I feel like my 5 also drains more than it should. As a comparison, I've been rocking a Moto X recently, and am at about 40% at the end of the day with that phone. I would still need to spot charge I think with heavier use, but I haven't come across that yet.
True, but my galaxy s3 drains at like 4% per hour when it's idle with good signal which is crazy! No apps running, nothing. Just sitting with the screen off. Also another thing, when you have a low lte signal, does it switch to 3G when it won't load anymore? My gs3 will keep trying to get lte signal but it won't and it never goes to 3G where it always has a signal. Very frustrating to have to go into setting and manually change it to 3G only.