In my current build, I have the fan on top of the cooler as pull, and it was by far the best config along with the bottom fans as intake and top fans as exhaust: https://smallformfactor.net/forum/threads/i-think-i-found-a-little-gem-realan-e-i7.6175/
A few things may have contributed to this result in my case (pun etc):
1) the side panel perforations do not cover the hole fan (only half of it), which really does not help when the fan is used as intake.
2) The bottom fans are very nicely aligned and adjacent to the heatsink. Without such fans, I wouldn't 100% vouch for this setup.
In sum, test for your case and see. My intuition is that pull would not be significantly worse, and it might even be better because it seems like in your particular case, the problem is that the heat is getting trapped. Using the fan as pull would be the shortest path for the heat to be exhausted out of the system.
EDIT: A few additional thoughts:
1) Pull may work better than you think in your case due to the orientation of the fan on NH-L12: in intake config, the blades are facing the fins, restricting the airflow for the fan. In effect, for your case, intake is pull, and exhaust is push. Fans do push better than they pull. So, while I am disadvantaging the fan in my setup, you'd be doing yours a favor (when you use it as exhaust).
2) I'd try and fit a slim 120mm fan there instead of the 92mm fan. Would make a difference (if it fits).
3) Definitely use an intake fan at the bottom if you can.
