This mob is very simple.
When you first enter you will more than likely run down the ramp and agro the whole room and go wtf. Then you will most likely try to range pull and and once again agro the whole room, and again say wtf.
the trick to this mob is simple if you tab target up you will see 4 tortured essences floating around the room. Pull one into the hall way it will pull one of the 4 roamers aruond the named. Continue to do this until all 4 of the roamers are dead.
For Ernax its real simple have your tank run into the room and to the right rest of the raid in the room to the left. This name comes with three types of ae's one which if not jousted can hit a little hard. Ectoplasmic Burst which is on a aprox 41 sec timer. This one is a magic based ae. We didn't know what to expect when we went in and our unexpecting raid members who got to close got a nice little blast.
The next ae is called Flash from Beyond its timer is on an approx 29 sec timer (more than likely that timers off, Pulled it once and killed it will correct down the road) This ae is magic based and did minimal damage to our raid force 8k max hit on members with out the greatest of gear. Heal through it.
Next ae is called Tempest of Torment this is a mental ae, and I have it on a 29 sec timer but this one is a dot so timers more than likely wrong. Again did minimal damage.
Other than that this mob is a good starting mob for this zone.
Enjoy