Tank
Begin the fight by having a Priest cast [Mind Soothe] on one of the adds on an end. The Main Tank walks down and aggros Razuvious at the same time that the Priest [Mind Control] takes effect, immediately taunting the boss and getting into position. The reason for this is to ensure that the boss will run to the MT instead of getting aggro on the raid.
The Main Tank should be available to [Taunt] Razuvious, using all defensive cooldowns, in the event that an Understudy add dies without the next prepared.
Off Tanks need to position where the Priests can use [Mind Control] without being in LoS of the boss' [Disrupting Shout] .
The Off Tanks need to be handling the Understudy adds which are not being mind controlled.
Damage Dealers
For the entire encounter, Melee DPS need to focus on maximizing their damage output on Razuvious.
Ranged DPS need to ensure that they are out of LoS from Razuvious when [Disrupting Shout] goes out. Use the railing on the top of the ramp to duck in and out of damaging the boss.
Healers
Priests needs to be assigned to [Mind Control] the Understudy adds who will be used to Tank the boss. Use a rotation to ensure that there is always another Understudy ready before one dies.
Assign Healers to the Off Tanks for the fight, who are handling the loose Deathknight Understudies.
Be sure you are out of sight from Razuvious when [Disrupting Shout] goes out.