For the first part of this fight if you are closer than 6 meters to the named you will have Detrimental Increments placed on those players. These increments tick rather fast and can not be allowed to reach 10. If they reach 10 your raid will explode. Melee players will need to joust these increments to keep them down. You will need to perform tank swaps as well to keep a tank on the named with out reaching 10 increments.
Once he starts spawning adds you will not have to worry about the increments any longer. This usually happens around 50%.
When adds spawn the only add you need to be concerned with is the "Worshiper". These adds will heal the named if left up for too long.
The second part to deal with the Worshiper is when the named is about to die. You can not have a Worshiper alive when the named dies. If you kill the named and there is a Worshiper still alive the Worshiper will sacrifice himself to the named and heal him between 50-75% of his max health. So, balance your raid dps and make sure you kill all Worshipers before you kill the named.
By the way, do not have a Repair Bot up during this encounter or up while you pull this encounter. You have been warned.
With regards to the adds, the "Worshipper" is not actually the one to be concerned about. Slightly easier tweak to the strat is that both a Worshipper and an Imp come in at the same time.
Focus fire the imp ensuring the worshipper is near to him when it dies and it auto kills the worshipper also.
No need to have random imps hitting people for the rest of the fight then.
The point at which the named heals if a worshiper is up is actually at about 5%. Also, during the second stage of the fight, he will occasionally call a name in red text. After a short time, the player called will die and be teleported to the entrance of the zone. So far, our only success in preventing this have been death saves on the victim. If a player is killed in this way and teleported, they can usually revive and make it back safely.
Tell your Raid Leader to not be scared.
i'm curious , what is happening with the bot ? my RL don't want to try it x)
Magic