Galaxy note 8 battery drain with mobile data
To be fair, I think this should be the expected result considering the device is using a lot of resources which are mostly power (CPU) hungry.


When using mobile data and additionally have mobile hotspot activated, you essentially utilising two communication radios (4g and WLAN) which themselves require considerable power.
It is mostly like there are some services running in background when there is an active internet connection. (e.g sync, silent updates etc)
This power we are talking about is coming from the battery hence it becomes very hot, just a symptom indicating it's "working very hard" to supply power to the device' resources and consequently a heavy battery drain is inevitable.
Although screen is considered to cause a high battery drain when the device is idle, its certainly not the case the the device is active and using its other hardware.


You may want to further analyse the batter statistics with other third-party tools from playstore (e.g battery drain analyser)

Also try to regulate the up-time of your mobile hotspot, to minimise battery usage.