I was having severe drain on both my watch and 12 mini. I unpaired my watch (watch was on watchOS 8.0 and phone on 15.0.2), let it sit for a few days, during which 15.1 came out, then, repaired, updated to watchOS 8.1, and battery on both seems to be back to normal. Screenshots of before/after (screenshot taken Sat 1:11pm):
Went from ~12hrs to ~36hrs battery life.
Went from ~12hrs to ~36hrs battery life.