I’m also experiencing high battery drain on a new (2 week old) XS Max. My last iPhone was a 6s+ and ventured to android after that. If I remember correct when the 6s+ was full charged it would hover at 100% for around 30/40 minutes before dropping to 99%..With the Xs Max I am getting to 99% from a full charge in approx 15-20 minutes with casual browsing.
I haven’t yet measured Screen on time for full cycle but I honestly feel it’s not even close to previous iOS or actual models. The drain is pretty consistent when it starts dropping from 99%