To be honest with you I think you've exhausted the list of browsers I'm aware of. Out of the four I think Chromium might the one I have had the most luck with. I would certainly be interested to know what the "bug" is.
The issue is maybe not so much the browsers but the device they are running on. The Pi 3 is by no means an underpowered device but loading webpages can be really resource intensive. I'm not sure what you are defining as content heavy but even on a fairly simple site there is multiple things that might need to be loaded.
Also worth keeping in mind is multitasking, having multiple tabs open at once can have a dramatic impact on overall performance. Try to avoid doing multiple things at once or in really quick succession. I wouldn't recommend having more than 5 tabs open at once in any of the web browsers. As you have discovered that requires lots of RAM.
In general don't expect the same web browsing experience on a Pi as you would a full desktop computer or even a smartphone. The Pi 3 is leaps and bounds ahead of the original model, but don't expect it to perform like a more powerful device does.