OS 1.0.5 for Star/Mars is out . I've just installed the update and the phone is getting warmer than usual.
I'm a little worried now.
Update:
The heating stops after a while , it's back to normal .
It takes 1-2 weeks before the battery drain reduces, then it becomes much better.
You can call up 'hey google' 'battery saver on' , that worked for me.
A few other things you can do to reduce battery drain.
1. Turn off screen auto-rotate
2. Turn off mi cloud sync
3. Turn off xiaomi interconnectivity
It's still higher than the older miui but now my battery can last over 12 hours at least.
My device is a 2 year old Mi 11 Pro on HyperOS xiaomi.eu.