For most guilds new to this fight, it will probably seem very difficult at first but it gets much much easier as you get used to it. The first thing you need to know is that you can’t tank Razuvious yourself. His normal melee attacks will pop you for 25k and if you manage to survive for a couple seconds, he can and will hit you with Unbalancing Strike http://www.wowhead.com/?spell=55470 which is a whole lot more damage and if by some miracle you survive that too, you are now susceptible to crushes and crits because your defense skill was lowered by 100.
To avoid going splat in extraordinary fashion, you must use the Deathknight Understudies that are in the room to tank the boss. In the 10-man version there are two understudies and two orb thingies (that have a name I cannot remember) which a player can use to control the understudies. In the 25-man version there are 4 understudies, zero controller orbs and a priest has to mind control the understudies instead. The understudies have a taunt on a 20 second cooldown and an ability called Bone Shield which reduces damage by 75% for 20 seconds and is on a 30 second cooldown. In the 10man, you are probably going to have two tanks in your group so it makes sense to have them controlling the understudies. When you use the orb it starts a 90 second channeled spell that puts you in control of the understudy so you will want the controllers to stagger their cast so that they don’t both break at the same time, leaving Razuvious untanked.
Start the fight by having one controller click on his orb while the other controller/tank, taunts the other understudy and tanks him for 5-10 seconds before clicking on his orb. Razuvious himself doesn’t become ‘active’ immediately unless he is attacked so the orb controller has a few seconds to get oriented and start attacking the boss. The controller will activate Bone Shield as soon as possible to cut the damage because Razuvious will be hitting the understudy just as hard as he would have hit a normal tank. The healers need to heal the understudy just like they would heal a normal tank. The second controller should be watching the first understudy and as soon as the Bone Shield animation goes away, the second controller taunts the boss and pops his own bone shield and they rotate back and forth like that the entire fight. If executed perfectly, the understudy will never be tanking Razuvious without bone shield.
When the channeled controlling spell ends after 90 seconds, just click the orb again. The orb will try to control the nearest Understudy, and if positioning gets weird and the understudy closest to the orb happens to be the one the other person is controlling, you will get an error saying ‘Target cannot be charmed’. To prevent that, you can taunt the understudy immediately after the channel breaks so that he runs over to you.
The 25man version can be a lot harder because you are counting on priests to do something they don’t normally do and mind control can be a bit tricky. For the pull, we have the priest that will do the first MC use Mind Soothe on his target so that he can get relatively close to it without getting aggro. As soon as the MC hits, the tanks all charge in and grab the other three understudies. As long as nobody attacks the boss, he won’t activate right away and the priest will have time to move the understudy into position so that when the boss activates and comes charging at the raid, he will have to run right past the understudy where he will be taunted.
The boss walks in a circle past each of the understudies so your best bet is to start the pull right as he is coming to the understudy that will be MCed first. MC has a 20 yard range and most priests don’t know how to use it well. I think the most common mistake is to assume that you have 20 yards from where the mob is standing when MC is cast, but that is not the case at all – if you MC a mob that is 19 yards away from you and you try to move it another 2 yards away from you, it will break instantly. And since any priest who has ever MCed something knows that it generates like a bajillion threat, the gut instinct will be do cast MC from max range. So, if you start the pull with an MC, you will want the boss close to the MCed mob already so that the priest doesn’t have to move the mob very far.
Getting the pull right is the hardest part of the fight in my opinion. 3 out of the last 4 times my guild has done the fight, something has gone wrong on the pull – either someone attacked the boss early causing him to run toward the raid before the priest was ready or maybe the priest just sucked, but I have felt the need to grab the boss before he goes and kills a squishy. The boss killed me every time within 3 seconds of starting the fight.
Once you get past the pull, it’s smooth sailing. Because you have more healers in the raid, it is a lot easier to keep the understudies well healed as compared to the 10man and because you have four understudies, instead of two, its OK if one or two of the die so the taunt/bone shield rotation doesn’t have to be perfect. The tanks will keep the 3 non-MCed understudies right next to the boss and try to avoid using devastate/sunder. They won’t be taking any dps so threat won’t be an issue at all, I like to drop a few shield slams and revenges and then drop down to white attacks only just to stay ahead of healing aggro. By doing so, they are taking as little damage as possible so that when they get MCed, the boss can beat on them for a little longer.
The boss has an ability called Jagged Knife that is randomly targeted and does a fair amount of initial damage and leaves a bleed on the target. Jagged knife has a minimum range of 5 yards so if you stack everyone on top of the boss, you totally eliminate it from the fight. He also has an ability called Disrupting Shout which does aoe damage to everyone in the raid and cannot be avoided. In the 40man version, Disrupting Shout also did a mana burn for 2x the damage it caused but you were able to use line of sight to avoid it. Disrupting Shout made positioning on the fight very exacting – healers/MCers needed to be in a place where they could heal/MC the understudy while being out of LOS of the boss while the casters needed to stand in a place where they could DPS the boss but quickly run out of LOS before a disrupting shout.
Once your priest get a hang of MCing and tanking, the fight becomes trivial. Until that point, it can be frustratingly difficult.