If we were to base our estimate on your low figure, that would mean a 10% drop in 30 minutes which would result in a completely dead battery in 5 hours if we started with a fully charged battery.
If we were to also assume (since you didn't provide any additional information) that this was 5 hours of screen ON time (at an undefined brightness level), along with a nominal mobile data and cellular signal, I'd say that's pretty acceptable performance.
If you look through all of the battery life threads you'll come away with a baseline of approximately 12 hours of total life, with about 3 of those hours being screen ON at minimum brightness, along with a nominal cellular signal and Wi-Fi usage.
Change any of those factors (brighter screen; lousy cellular signal; mobile data connection rather than Wi-Fi; etc) and the battery life will decrease accordingly. The big screen and a lousy cellular/mobile data signal are the biggest battery consumers.
Regarding your charging complaint, I'd say that your results are atypical - I usually see the battery go from about 20% to 100% in about 3 hours (I make it a point NOT to run the battery down until it's dead). Of course, my phone usually charges while I'm sleeping so I don't care if it takes 3 hours or 5 hours.
Edit: here are my battery stats from today if you care.
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