This is NOT my original work. All the real credit goes to some guys in Russia as best as I can tell. I merely google translated their work and cooked up my own method for rooting (which is a bit easier than what they recommend). You can find their source materials here: Russian Lenovo Website - Phab 2 Unlocking the bootloader thread.
Grab the latest version of SuperSU from Chainfire (https://download.chainfire.eu/696/supersu/)
Download the version of TWRP I found on the Lenovo Russia website here (it is attached to this post)
Copy SuperSU to your Phab 2's SD Card (it can go on either the internal or an external drive) (ADB push SuperSUxxx.img /sdcard/)
You need to unlock your bootloader if you have not already done so:
adb reboot bootloader fastboot oem unlock
Now that we've got a good clean operational unlocked bootloader let's apply our new recovery:
adb reboot bootloader fastboot flash recovery TWRP-PB2-650_3.0.2.img
Press the center of the volume rocker (both vol+ and vol- need to be depressed) and at the same time hold down the power button until your Phab 2 posts. You'll know you did the procedure right because an ASCII arrow symbol will be scrolling through the device's 3 boot options (Recovery / Fastboot / Normal).
Release the power button and roll your finger holding the volume rocker to the volume up side of the rocker. Release the volume button.
Press Vol+ until Recovery is selected (it is the first option)
Press Vol- and wait 20 or so seconds for TWRP to load.
You now have to decide if you want to make TWRP your permanent recovery. If so, mount SYSTEM as RW and using TWRP's Advanced File Explorer navigate to /system and either delete or rename recovery-from-boot.p (I renamed mine to recovery-from-boot.p.save).
Go back to TWRP's main menu and select INSTALL. Navigate to the SuperSU image you copied to storage at the very beginning of this guide and flash it.
When you're done, reboot.
Don't panic when your Phab 2 bootloops once. It'll boot fine on its second pass. In another 20-30 seconds you will be greeted by a fully rooted Phab 2.
Enjoy! Screenshots are attached to the second post.