Also, the infernals each despawn after a few minutes; the Prince will not cast Enfeeble on your tank; he'll aggro if your threat goes even a single point above the tank's; and the whirling axes in Phase 3 don't hit very hard.

I recommend that healers flask for mana regen if they're learning the encounter. It's a long fight.

Lastly, unlucky infernal placement can ruin your chances, because their Hellfires will sometimes overlap, with your raid standing in the middle -- unable to pull back without going out of range, and unable to move in without being in range of his shadow nova. We've had the best results from tanking him against a wall, with the ranged people halfway between the Prince and the entrance. Infernals seem to drop on us less often.

If one does drop on you, you have to move immediately, because the Hellfire ticks for major damage and getting hit with Enfeeble at this point will kill you pretty much instantly.

I recommend as little melee-range DPS as possible, until your guild is experienced with the quirks of the encounter.