I don't think the problem is with the phone. The batteries are just crap. I work at a service center and by far the best-selling batteries are Samsung ones. Lots of people coming in with bad batteries on Samsung phones.
We have noticed a trend, i can confirm this with my own devices and also confirmed with friends that own Samsung phones - batteries that say "Cell made in Japan" or "Cell made in Vietnam" hold up good, while those that say "Cell made in China" bloat quickly and die.