seems like S8/+ has quite a few hardware issues, dont know its because of the unoptimized software between the OS and apps or memang hardware problem..

These are the prevalent issues so far (can be seen on reddit and xda of many users complaining about it):
1) S8/+ glass (front and back) very easy to pick up scratches compared to previous generations.
2) S8/+ fingerprint sensor also gets scratched easily (not glass)
3) S8/+ red-tint displays
4) S8/+ camera's OIS gets stuck quite often, have to shake the phone quite roughly in order to "unstuck" it.
5) S8/+ LED dying out of a sudden issue
6) S8/+ random sounds cuts from the speakers
7) S8/+ randomly rebooting.
8) S8/+ random vibrations after unlocking the phone via hard-pressing home button. (like it doesnt register immediately when you're pressing the home button to unlock, so the vibration comes later after u unlock the phone and touch anywhere on the screen)

then there's a plethora of software bugs between the OS and certain apps.
1) edge lighting not working with certain apps
2) facebook zooming in/out the wallpaper when exit the app
3) whatsapp LED notifications not working sometimes
4) whatsapp images received when open it, its zoomed a little.

Hmmm, my experience with the S8 is quite the opposite actually. Of all the Samsung devices I've owned before, this one seems to be the best in terms of standby power consumption. Could it be something to do with Android Doze? Anyways, the standby time is not spectacular by any means, but for a 3000 mAh Android device from Samsung, this one has better battery performance compared to the Note 5 which I previously owned.

you using dual sim?

i see. im using dual sim,so far so good,but i dont play game on my phone and no game installed. maybe give it another day or two to see how. 

That's really strange. It's like a 1% drop in standby in less than 5 minutes? Mine doesn't drop that much and it's a regular S8 and not even an S8+.

Install GSAM battery monitor to trace down ur usage, simple as that. Never failed me in tracing my battery standby drain.

My primary battery standby drain due to bad telco (UMobile) reception. 

Remember to to enable battery stat access for it.

That's why u need GSAM phone signal graph to trace on the telco signal. App battery drain is monitoring & controll by Samsung App power monitor so it won't make big impact.

Poor reception is not minor problem, it could drain ur battery faster than u can imagine compared to apps. 

Why keep checking. Don't check and removed all those nonsense battery checking apps. Use it as normal.

After few days you will notice it actually great in battery. You keep checking sure it get even worst as you keep turn the phone on and off for nothing include waste energy for those battery checking apps.

You notice or not seems only you complain on the battery performance now.

It learn your usage behaviour, if you keep on off for nothing, it can't learn.

I used that, but sometimes bixby still pops out. Basically what that app do is launch bixby, close bixby, open new app in quick succession.

I just use package disabler pro to just disable the bixby button. Down side is its just a useless button now lol.

am fot fan of thick² case. ruining my expensive phone design 
dat app is old news & it wont be fast bcos it always hook to real Bixby app. same goes for other remapper.
use package disabler with cautious.

real bixby will popup occasionally especially in lockscreen mode & it goes slower when bixby need to relaunch once stopped by system or manually.

just tested, not working on my S8+.

already toggle to on already, i even restart the phone.  But press the button, it still activate Bixby. 
past few months was bad but i think they just upgraded their 4G coverage near my workplace at Senai.  I can get 77Mbps download. 

Still different as iPhone, iPhone mute is real awesome mute everything included gaming. I very miss the mute button where mute all gaming sound in iPhone.

Perhaps can submit complaint to Samsung.

Samsung store is really cheating one..
From the previous Note 7 also like that..
That's why most of us get from Maxis