Yea, I know this is kind of off topic but, The phones have been upgraded, multi core CPUS, bigger displays, more memory and these chips are all 100% faster than phones just 3-4 years ago but, one thing we have not changed or had any new tech in is in battery tech. We are still using the basic battery layouts as we used 3-4 years ago. I dream of a day when I only need to charge my phone once a week, with heavy use....
Maybe I just need a Nuclear power plant in my pocket but, this is one are I want to see a major step up in...
As for battery problems in Windows Phone 8/8.1, Check your apps that are running in the background, It could be one app polling for data that could be killing your battery, also, if your in spotty coverage area and a app is doing this. Go into Settings, slide over, and look over background apps, disable all for a test, Run you phone for a day to see how battery is, then enable one by one till you have a drain problem.
This is normally a App problem and can cause a headache with some people. I disable all besides a few apps that I use a lot of, like weave, my weather app, and one more but, everything else is disabled. On my 928, I can get 2-3 days with light use but, on a heavy use day, I can get through 95% of the day with out neededing to charge...