Here here, went there, tried there, temps dropped by 2c, the stock cooler is even smaller than the ones the came with core 2 duos back then and c2ds had 65w tdp.
as for OP I even don't know what app he has used to monitor temp and what's his vcore - many people use speedfan to monitor temps but that's not very good has several bugs and needs to be properly calibrated first.
I've asked OP to post his vcore using cpu-z screenshot or from bios - sometime when using a stock HSF temps can be reduced by lowering cpu vcore voltage.
you've used bios or some fancy asus apps to monitor cpu temp or you have used some app like HWmonitor/Realtemp/Coretmp which can measure the temps more accurately. What's your cpu vcore and what app you have used t load the cpu to the maximum limit ?
Granted stock HSF is not good like U12P but stock HSF should keep the temps below 70c when not OCed and while playing games cpu load is rarely 100% all the time - so temp should not cross 70c if the HSF is properly installed and paste is applied correctly.
I've one of those Intel Pentiium D 930 CPU - you know how much they were criticized for heating issue - after I properly installed the stock cooler with CM nano Fusion load temp never crossed 60C and idle temp was around 40C in the summer time.