Yes, these batteries are doomed.
I have been looking into the charging PMIC and if you can tell it to stop charging at 80%, but it appears to be hard set at 4360mV where it goes into a trickle charge mode and runs the phone of the USB power.
The problem is two fold. For one thing we have a 2100mA battery, and the charger is 900mA, so a 0.5C charging is good for long term battery life, even better if you charge over USB at 500mA. But the discharge rate can be as high at 1000mA if you have all the bells and whistles on and things are hot to begin with. The typical usage with screen on is 200mA, maybe 400mA with WiFi, more with BT. But current increases greatly when both cores are over 1.5GHz.
So the problem mostly seems to be the charging is reducing capacity by people going below 10% charge (if you graph the voltage you can see the tail off below about 15%) and charging above 80%. LiIon capacity is reduced by keep over 95F and also permanently reduced by draining to low voltage levels and also charging much above 4.2V and then holding the voltage there. I noticed the capacity after two weeks was reduced by 20% already.
And no, the thermal runaway is no longer a problem and I wouldn't mention it anymore. The battery self-protects, as well as the system is being very careful monitoring the thermals. Also, the CPU is throttled above 56C ( I believe)
But, I know in the PMIC controls you can disconnect the battery and run only on AC when plugged in. This would be ideal to leave charge the battery to 80% then stop charging it, and you could leave it plugged in at work or overnight without worrying about the battery capacity.