Also remember battery percent meters are not exactly precise, and discharge rates on the meter can very at different levels of charge. IE using 10% of the actual power starting from 100% may show up as 8%, or 12% using 10% of the actual power starting at 50% may show up as 8%, or 12%. This can vary by phone and by battery.
Here is what I would suggest. Stop worrying so much at the moment. Trying to judge 2 - 5% drops here and there will get you no where, especially as battery meters in phones are not specialized scientific equipment and diffrent batteries will appear to discharge at different speeds at different levels.
This is still a new phone and new battery that may settle down over a little time. I would take these steps...
1. Plug the phone in to a wall charger over night to get a good charge. Unplug it int he morning and take the charger with you. (Hopefully you will not need to forever, just for now)
2. Use the phone as normal through out the day, not obsessing over every percent of battery drop, not looking at the battery charge every 5 minutes or even 30, just glance at it when you use the phone for other things, and then only at the standard meter to see if it is about to die.
3. If the battery gets to red on the notification bar, plug it into a wall charger for a bit. Note the time mentally, but not obsessively.
4. Plug it in over night again.
5. Repeat for at least a week and see if it is working at a reasonable level. This will give the battery time to settle in and you time to figure out how its working and if it's working for you.
6. Think about when you use the phone, when it discharges and when good times to charge are. For me, If I charge at night it will USSUALLY last the day at work, unless I use it an awful lot more then normal. I plug it in on the drive home (car charger) I have a bit of a drive, so this gives it a nice kick for the evening. Occasionally I need to give it a little juice during the day if I use it a lot, I keep a second charger at my desk for that as the USB to computer does not charge fast, but in a pinch I'll use that too. I rarely use wifi, and am on 4g most of the day with varying signal strengths.
7. If after a week it still seems off, run it from full charge in the morning until almost dead, under normal usage and then post all the graphs here again so they can be compared. Posting a full discharge will give a lot more info the just 30 minutes, due to the reporting fluctuations mentioned earlier. If it looks drastically different then others when comparing screen times and signals to battery life, then take it back and get a new battery. If it looks normal, but you can't deal with the need to charge during the day (many jobs that doesn't work well with) and you use it all up to fast, look at a bigger battery, or a phone with better battery life. I think you have 30 days to take it back if your not satisfied.