I tried it on my LTE Tab Pro 8.4 which had the latest firmware for my region "BTU" which is NB7,
It wouldn't work, but another XDA member @Inuit, said it worked for him with the DBT NE5 firmware he has on his device.
SO! I downloaded the DBT NE5 file, extracted the Kernel and repackaged it and flashed the Kernel on it's own. Then tried the root method.
I have now successfully rooted the device and kept Knox at a cool 0x0.
I chose to do things this way, as I wanted to keep my regions firmware and not that of another county.
So I still have my original firmware, but I am now using the newer Kernel, everything seems to be working fine but considering I only did this 15 minutes ago, I haven't had enough time to test. But connectivity is fine, battery levels fine etc...
UPDATE: Everything is fine for me, loaded Xposed modules, no adverse affects at all
I have attached the repackaged Kernel, all you need to do, is go into download mode and flash the file under the "AP" Tab in Odin 3.09.
Then install the TowelRoot app, which you can get from the links in the thread below:
Install the latest, SuperSU (again links in the above thread).
You should be rooted and Knox kept at a cool 0x0.
I have tested the this on my Device the T325 and another user tested the Kernel for the Wi-Fi version T320 and are working fine But!
You try at your own risk!
Download links below
TR Rootable Kernel for LTE 8.4 SM-T325
Original NG1 Kernel for LTE 8.4 SM-T325
TR Rootable Kernel for Wi-Fi Only 8.4 SM-T320
Original NG1 Kernel for Wifi Only 8.4 SM-T320
TR Rootable Kernel for SM-T525 10.1 LTE SM-T525