it also depends on how you use the laptop,
for example if you constantly let it run under hot temperatures, it can degrade the battery when you use graphic intense application or games. you can get a cooling fan under, to keep temps better.
also if you charge it and then use it up to zero percent and recharge again , it degrades the battery as well.
but most likely you probably got a bad / lemon battery , but if it keeps happening it could be a bad model.
I don't play games (well, I don't have time for Heroes of the Storm anymore). Most of the heavy use is from Android Studio, and everything else is offloaded to my server. But seeing as how it's behaving, I might offload Android Studio to the server as well.
Got the battery replaced yesterday from a 3rd part - it seems that when the thing is plugged in and close to 100%, it slightly discharges a little bit.