Just curious but my S6 battery life is horrible too. How is your battery life?
My experience personally has been good, very much in line with my expectations (
refer to this example, with screenshots). I'm not what I'd call a heavy user though -- people who need to spend a third of the day or more on their phone likely have usage patterns that exceed what the device can deliver on a single charge. Samsung included fast charging to help mitigate that, but judging by the abundance of negative comments here on the forum, for some folks it just isn't enough. Many seem to expect it to be an all-day device regardless of usage variance or operating conditions (accounting for signal strength, etc). For some, it just isn't. For my use, it's more than adequate. (For heavy-use days where I'll be away from an outlet, or while traveling, I just bring along an external battery pack.)
The only reason my average drops is if I'm gaming -- resource-intensive games like Hearthstone, for example, can consume 5-10% of the battery per match, depending on game length. If I'm just making calls, browsing the net or listening to music, using social media apps, (as in the screenies provided) I almost always post more than 5 hours SOT on a charge. I should note that's with good coverage & signal strength in my area.
Based on your opening post, it sounds like you may have a defective unit; as such I wouldn't make any quick judgments about poor battery life until you can get it sorted or exchange it for a properly functioning one.
Edited to add: If you think your usage needs go beyond what I've described (or results posted by other users who have similarly positive experiences), you may wish to consider swapping for a different device that will accommodate them.