I find ones battery life largely depends on ones reception quality. Semi low reception for a prolonged period drains batteries like crazy. No matter what app strain one puts to it.
So true. I detailed so many variables tha can affect battery drainage speeds in a post long ago, and it really hampers accurately gauging you battery life to the point where I feel a single data point in drainage is worthless.
After many cycles, I've noticed that it can vary by a huge margin. My battery life appears to be 5-10 hours with the biggest factor being whether I'm on wifi or not (aside from audio listening which doesn't use much battery life, but counts as usage - you can make your usage time appear to increase if you listen to a lot of audio). On 3G, it's closer to 5, on wifi it's closer to 10.
Cell data is supposed to be 8 hours. So do I have a broken phone? I doubt it. I gather that it's probably largely due to the 3G reception and usage in my city. We have no lte, but however it works I think that's just how it is. People should not really listen to others when they say "oh I get X hours, your phone must be broken" - you should really compare it with phones in the same area. Not saying that broken phones don't exist, but just consider the wider sample set before jumping to conclusions.
Not just reception either. I've seen my phone vary in usage times according to all sorts of parameters. I've seen my phone drop 10% in 30 minutes. Heck I've seen my phone drop ZERO percent in 40 minutes. Not to mention I doubt the percentage meter is fully accurate and is likely not truly linear. So many factors.
The only thing I will add is that the iPhone 5 has decent battery life for my usage - it gets me through the day. Probably best thing you can do if you're picky about this sort of thing is to turn the percentage meter OFF and just use it and see how you go.