I could be that you just have your gear ratio wrong for your application and driving style.
the 7.3 gear ratio is given for road course racing applications.
For drifting you might want to try to play around with your gear ratio a bit.
If you are concerned that it is damaged... have you ever had to give it a push start or anything of the like? If the motor can spin under resistance at very low rpm you probably haven't damaged the ESC.
If you are still concerned about the heat you can put a fan on the ESC and that will keep it cooler and prevent most damage from occuring.
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