Bottom line, battery life has gone from great to terrible. The initial iOS 13 release wasn't too bad, but the iOS 13.1.2 release had a serious battery bug. While this bug was subsequently fixed, this latest release seems to bring back this bug. Battery life is now so bad that I can watch my battery life ticking down while I'm browsing the web, composing an email, or using Twitter.
Interestingly, background battery life -- when the device is locked and not being used -- is not too bad. Also, while not as bad, iPadOS 13.2.2 battery life is also much worse than post iPadOS 13.1.2 releases.
The Zendure SuperTank
The problem doesn't seem to be down to specific apps, but instead seems to be a widespread operating system problem.