Not sure if this works in 1.12, but it worked in 1.11.
You need 2 hunters that are decent at kiting to do this.
Assign each hunter to each of Thekal's guards, and have them pull them. Have the main tank grab Thekal, and have him tank him. Don't DPS him down yet.
Have the 2 hunters pull the 2 guards to the ZG entrance, then have them feign death. The 2 guards will evade back to their spots. DPS Thekal down, kill him, and collect your loots!