I was just going to start a post until I saw your thread. Mine has been HORRIBLE after the 2.2 update. Did you ever find a fix?
I updated my phone to 9.3 (now 9.3.1) and the watch to 2.2 on the same day. The next day, my watch asked to go into power saving mode by 5pm, not even off the charger for 11 hours. That's the first time I've had it not last a whole day since I got it. And that's also without doing any exercise activities.
I've checked settings, uninstalled apps, and I've done a backup then unpair an re-pair with my phone restoring from the backup and the same horrible battery life. I haven't tried pairing as a new watch because I don't want to lose all of my achievements.
I've noticed my phone is having issues connecting to the watch sometimes too. If I go to the watch app, then to Passcode, it'll usually tell me it can't connect to my watch, even though both the phone's bluetooth and the watch show connected.
My next step was going to be wiping the phone and restoring it from my current backup.
Any other suggestions?