Derzith is one of three linked, named skeleton mobs in the area of this zone called The Grand Theater ( 14, 8, 180 ) /waypoint 14, 8, 180. The other two mobs are Xe'ziza of the Jarsath and Thera'ta of the Jarsath. For the purposes of this strategy, they are nicknamed "T","X",and "D". (Their names are hard to pronounce so this was the easiest way to decipher them.) Derzitha of the Jarsath for example is named "D".
If any one of the mobs runs to the stair way that you used to get into the room, they will drop attack and go back to their original spots. If you are close to killing them and this happens... you must start all over again. Though if you're about to wipe and can make it to the stairs, it is a good chance you will live.
Every time the mobs reset back to their original spots, they change positions of where they each stand. You want to get the formation with "D" in the back and "X" and "T" to the left and right of the carpet.
The carpet is a safe zone. Stay on it and the mobs do not gain aggro, (this is before the fight). Step off the carpet to the left or right and you will trigger the mobs.
Two healers, a mezzer, a tank, and 2 serious DPS players are recommended.
If you lack crowd control then the order of attack should be T, D then X.