Nightbane's tactic

Last boss of karazhan!!

[edit] Ground Phase
The Ground Phase lasts from when Nightbane lands until his health hits 75%, 50%, or 25%, at which point he then takes to the air for the Flight Phase. All during the Ground Phase Nightbane casts Charred Earth, Fears, and Cleaves.

Tanking Nightbane
Tanking Nightbane is a fairly straightforward affair, with the exception of fear. Handling fear is paramount to success, as one or two uncontrolled fears will guarantee a wipe. Warrior tanks can minimize the effect of fear by stance dancing. Having a macro to avoid fear really helps. For the Druid or the Paladin tank, however, things are not so easy unless Fear Ward is present. Patch 2.3 changed the cooldown of Fear Ward to 3 minutes, making it difficult to rely on by itself for the encounter. But since Nightbane will chase the tank even if the tank is feared, raid members can run out of range of the fear to avoid getting caught by a cleave or tail sweep. A tremor totem in the tank's group is a huge help for this strategy by reducing the amount of time the tank gets feared.

Everyone else
Healing in this phase is not particularly difficult, with the fight resembling a simple tank and spank, but be careful not to rip aggro with an early heal on the tank. Nightbane has a lot of burst potential when his melee is combined with his cleave and smoldering breath, so healers need to be somewhat awake, even though they can get outside the 5 second rule quite often.

Another ability that might be problematic during the Ground Phase is the Charred Earth. Assuming it appears beneath Group 1, Group 1 should briefly shift over to Group 2's position until the area is safe again, and vice-versa. Occasionally, both groups may fall victim to Charred Earth at the same time—if this happens, all healers and ranged must temporarily shift forward to remain in range of the tank and the boss. Consequently, both groups will be closer to the boss and vulnerable to the fear. The tank must be ready to take preventative measures as required should the raid's healers suddenly find themselves incapacitated. When melee DPS are avoiding Charred Earth, they must be careful not to move into the area vulnerable to Cleave (ahead of his front legs) or Tail Swipe (behind his back legs). Any melee-type wandering into his head area are prone to being one-shot.

This is a long, healing-intensive fight that can last upwards of 10 minutes. Timed correctly, many mana-regenerative cooldowns such as Innervate and Shadowfiend may be used twice during this encounter.

Flight Phase
Nightbane flies into the air, signaling the start of the Flight Phase. Flight Phase lasts until Nightbane has finished using his two abilities of Rain of Bones and Smoking Blast.

Preparing for Smoking Blast
Immediately after Nightbane summons skeletons while in his Flight Phase, it targets the raid member with the highest threat and repeatedly casts Smoking Blast on this target. This is typically a healer.

Smoking blast deals physical damage, so the more armor the target has, the better. Paladins would be ideal; however, due to their mechanics, it is very difficult for them to have the highest threat. Even if paladins have improved righteous fury, their healing threat generation is only 0.5*1.9=0.95 compared to the 0.7*0.8=0.56 threat (Priest or Druid with blessing of salvation, 0.595 for a Shaman) that the other healers will have. In general, it is fairly difficult for the paladin to compete with healing aggro for Smoking Blast against priests and shaman who have AoE heals.

Healers must be prepared to spam heals on whomever the affected primary healer is. This will likely occupy a majority of your healers' time, which complicates dealing with the skeletons. When formulating a strategy for killing the skeletons, remember that your healers are otherwise occupied.

Alternate Method #1 This method requires a Resto Shaman with Earth Shield. When Nightbane takes off, have the Shaman place an Earth Shield on the tank. Once the Rain of Bones begins and the skeletons start to spawn, have the tank grab aggro on as many of them as possible (Thunderclap [improved talent works wonders here] for Warrior tanks, or Swipe for Feral Druids). The skeletons will proc the Earth Shield on the tank, thus generating the healing aggro on the tank. This will limit healing in multiple ways, 1) only one to three people actually taking damage from Rain of bones, 2) Earth Shield will keep the tank up easily provided the resto shaman's gear is decent, 3) the Smoking Blast will only be hitting the tank with the Earth Shield (which will in turn proc it more). You can drop a Tranquil Air Totem if the tank is not in the healers' group to ensure that healing can still go out, but Smoking Blast will hit the tank.

Dealing with skeletons
All healers and ranged collapse to where the main tank is standing in order to avoid the Fireball Barrage. Once Rain of Bones starts, all players must immediately move away to avoid taking too much AoE damage. Five skeletons will spawn during the Rain of Bones. These hit fairly hard. To mitigate this damage:

Warriors and feral (bear) druids should use taunt and cleave/swipe liberally to keep aggro off of the healers. Warriors can use Challenging Shout and Druids can use Challenging Roar, during one of the phases. Grenades also work very well to establish initial aggro.
Pets with taunt abilities (especially hunter pets) can hold aggro temporarily
Paladins are uniquely suited to this phase. A Paladin should activate his DPS cooldowns from trinkets and avenging wrath and tank the 5 skeletons. The primary advantages of this strategy are that all skeletons are controlled during the Flight Phase and will not run about killing the healers, skeletons die much faster due to the AoE and all healers will be able to get the Blessing of Wisdom buff to help mana issues instead of the Blessing of Salvation buff. Warlocks and mages can then begin AoE and down the skeletons much sooner than single target DPS allows.
Shaman can drop Stoneclaw Totem or Earth Elemental Totem to buy healers an extra second or two
It also helps in the group spreads out a little bit after gathering, so the tanks can identify who has aggro from a skeleton and pull aggro from them as soon as possible. Note: Do not spread out too far as this will make pulling aggro from the skeletons even harder.
Hunters can drop Frost Trap on the skeletons to keep them anchored for a tank, which can be a huge help. Entrapment spec is a plus.
Lacking a good Paladin tank, it may be be more effective to kill the spawns one at a time rather than AoEing them. Be warned: Due to the Smoking Blast occupying the healers, there isn't much chance for survival if a mage or warlock draws aggro from AoE.

Also, If you are still having trouble with this fight being the Skeletons still are not going down fast, people are dying or its killing the healers mana, It might be an idea to have your raid pre-prepared with Stratholme Holy Water from the Undead side of Stratholme. Using this when all 5 are up will deal decent damage, and if everyone that can't AoE uses this they should go down much quicker.

Transition to the Ground Phase
Ten seconds before Nightbane lands, all members of the raid should fall back to the previous positions, dragging whatever skeletons are still alive with them. Ideally, all adds will be dead at this point, but having one or two still up before Nightbane descends is fine. The tank must remember to keep an eye on the casting bar, and stance dance to avoid an early fear. A recent change has made this fight a bit easier for raids that do not have fear wards/tremor totems/warrior tanks. Nightbane will keep aggro on the tank, regardless of whether the tank is feared or not. This introduces the challenge of the tank being feared into the ranged group, but it does make paladin and druids tanks more of an option.

The most dangerous parts of this fight are the transitions between the Flight and Ground Phases, when the main tank must reestablish aggro. Hunters' Misdirection is especially useful here, to make sure the boss goes directly for the tank.

Ground Phase begins again when Nightbane lands, rinse and repeat at 50% and 25% until victory.