The issue is each release has different problems for different people. iOS 10.3.3 has been awful for me, my battery life took a HUGE dive with it, 3-4% loss in less than an hour with the phone just sitting on a table. With iOS 11 still being in beta and tweaks being made it should be expected that things go wonky, it's a beta after all. 10.3.3 should not be draining battery like that though, that's just not acceptable but .. it's the world we live in.
I have noticed that battery drain is most of the time caused by either Location Services or an app badly developed that doesn't behave properly. If when in Standby you notice that the battery is draining fast, check for those two possible causes explained above.
There have been days when while in Standby for several hours, the battery of my phone was barely used.