I have exactly the same problem. After updating to 14.2, my iPhone 7 Plus experienced a severe loss of battery performance and drains much faster than it did prior to the update. I have done everything I know of to save battery life (turning off notifications, reducing screen brightness, turning off background app refresh, turning off location services, etc) and the problem still persists. This is definitely due to the update since my phone was working fine before that and is now barely usable. This needs to be fixed right away.