I did exactly what the post said, didn't change a thing.
Now my problem isn't the same as yours. My SP8 doesn't overheat, and battery life isn't as bad as 2 hours.
However, I have set a lower CPU max, I have enabled battery saver mode, I have set screen brightness to 15% (which is hardly usable on a bright day!) and it STILL only gives me about 6 hours of use, when Microsoft markets it as "up to 16 hours". There is NO WAY this machine will last for 16 hours in any kind of usable state.
What did they do to get that estimate, turn off Wifi, set screen brightness to 0% and set to idle?
This is an expensive machine that is targeted at people on the go, not as a desktop replacement.