Earlier quoted context omitted.
I run mostly dev tools, text editor, etc. But I have a bad habit of having more than 50 Chrome tabs open, and Chrome is a notorious pig on just about every OS. My Macbook Pro (2011, quad core i7) is famous for heating issues, but that aside, any app that forces use of the discrete GPU (at one point, even Coda did) would cause the fans to spin. I don't want to sound like a snob, but the 13" MBPs aren't comparable with…
Previously to this machine I had a 15" MacBook Pro (2012) and didn't have any issues either. I don't run many browser tabs, that might be the difference. Although I do think the fans spun up more often on the 15" you're right.
Apple was basically in denial about the issue until last year when they issued the repair order.
Having said that, most of the quad core models will get hot pretty fast, especially if you use something like Chrome. If you use Safari, you probably won't have those issues, as it's much more efficient than Chrome, but that's a preference thing.