This could be the first time a Blizzard representative offers strategy tips. Eyonix shared details of what to do against Prince Malchezaar in Karazhan:
Eyonix: “It’s important for your tank to use shield block as often as possible during this entire encounter. Also, ideally shield wall is being saved for specific points where emergencies are likely to occur (i.e. having to move during phase 2).
Demoralizing shout should be the preferred shout. As a matter of fact, any spell or ability from anyone in the raid that grants the tank additional damage mitigation should be used.
During phase 2, all healers should be spamming the tank, keeping him/her topped off completely. Everyone else should be mindful of their own health during this phase. Outside of keeping the tank alive, this fight is about watching the environment. Do not wait until you’re already boxed in to move the raid. If you look around and there is a place that an infernal could potentially drop that would block you in, move accordingly at that time.
Tanking him by the entrance to wall near the left works well. Raid marking one ranged player for the rest of the ranged (including healers) to follow when that portion of the raid has to move can be helpful. It’s always important that your raid leader is helping others to watch the environment. The designated raid leader should be paying attention for others, and providing instructions during the course of this fight.
I do not agree that luck has as much influence over this fight as some perceive. A group can still easily adapt to bad infernal placement, and the tank can easily withstand the crushing blows in phase 2. This is assuming everyone is paying attention, and detailed instructions are being communicated via voice chat (if your guild needs such instructions).
Just be prepared for an infernal to land on either group, and always know where you plan to move. There is plenty of time in between infernal drops to know where you may need to move should your group be the landing point for the next infernal.