I've been trying to root my Galaxy tab 3 (i think 4.2.2) for a while and recently did it. But after I installed supersu from TWRP, my tab wouldn't boot normally and would keep looping. I tried flashing the firmware back and rooting it again but it didn't do anything. I appreciate any ideas.
SuperSU sometime gives many bootloops while booting first time. But if it is in bootloop for a long long time then apparantly you have flashed a wrong version.
I will recommend you to flash MagiskSU . It works every time for me.