Zul'jin is split into 5 different phases. He changes phase at 80%/60%/40%/20%.
First Phase - 100% health
The 1st phase is his troll form as shown in the above picture. Do not stand in melee range of Zul'jin because he has a nasty whirlwind ability. Zul'jin also has an ability called Grievous Throw that hits a random player for about 5k damage, and leaves a bleed DoT on the player that ticks every 2 seconds for about 2.4k damage. Grievous Throw is non-dispellable, but will be removed when the player gets healed full.
Big heals on the person who gets hit with Grievous Throw! Zul'jin's melee is quite weak on the tank. It is the responsibility of the tank and the melee group to get out ASAP when Zul'jin does Whirlwind. Use your Nature's Swiftness to heal the person with Grievous Throw if you have to.
Typically, this fight is done with 3 healers. Depending on what your raid leader wants, generally 2 healers should be on the Grievous Throw victim, and 1 on main tank.
Put out a searing totem close to Zul'jin when he is getting close to 80% health. Aggro resets during phase change! Let the tank know where the searing totem is at and the tank will stand there during phase change (call it out on Ventrilo).
Second Phase - 80% health
Zul'jin becomes a bear. Zul'jin now deals massive damage during this phase. Only the tank will stand in front of Zul'jin while everyone else stands behind Zul'jin. All healers should heal the tank. Zul'jin will do a 6 second AoE debuff that if it does not get dispelled, it will deal huge damage and stuns the player who did not get dispelled. This is not your field so you can't do anything about the dispels. If your group does not have paladin or priest, might want to pass on this fight because it is extremely difficult to survive through the stuns. If the tank gets stunned, it is usually a wipe.
If dispels go well, just focus on healing the tank. Zul'jin's bear phase hits extremely hard!
Third Phase - 60% health
Zul'jin becomes an eagle. There are no aggro table here, and Zul'jin stays in the middle with no melee or spell abilities. Call out on vent to let other healers know where you will be standing during this phase. Good positions for healers would be the left, right, and top of the stairs.
Zul'jin spawns 4 cyclones onto the stage, and they randomly follow players. If the player gets hit, it deals around 1k damage and knocks the player back a bit. There is no duration on how long the cyclone will follow a player. They have a life of their own.
A debuff (aura) will be placed on every player during this phase. Each time you casts a spell, you will get struck by lightning for around 1.2-1.3k nature damage. This includes water shield! A good tip would be to casts big heals only, and only heal players who are below 50% health.
*note* - if you cast an instant spell as soon as you finished casting a spell (healing wave), such as replenishing your water shield, you won't get hit with the lightning twice.
Make sure to spread out, it is best that you stand on the edges. Don't run near the middle because the melee wants to do maximum DPS while trying to run away from cyclones. If you run in there, there is a chance that you will drag a cyclone into the melee group.
Fourth Phase - 40% health
Zul'jin becomes a lynx. Tell everyone to group up by the tank because it is the easiest way to heal through Zul'jin's insanely quick abilities. Zul'jin's lynx phase is all melee and he has no cleave ability so just group up on the tank.
Claw Rage - singles out a player and attacks him 12 times in 6 seconds. Does not matter if you are top or last on aggro because Zul'jin randomly targets a player to use Claw Rage on. First few hits are weak, but the damage stacks up because it leaves a debuff on you per hit so the last few hits deal massive damage. Zul'jin will pause a second in front of the person he will use Claw Rage on, so you should put earth shield and start healing waves on that player!
Lynx Rush - Zul'jin will attack 9 times and each time will hit a random player or the same player multiple times. No matter how much aggro you have, this ability chooses random targets. If everyone is standing by the tank, simply use chain heals to heal through this ability.
Fifth Phase - 20% health
Zul'jin becomes a dragonhawk. This is the hardest phase and careless mistakes will easily kill players. This is the phase when you use your cooldowns (Bloodlust). Use fire resistance totem! (The phase change takes a couple seconds so wait till tank can start building aggro before you use bloodlust.)
This phase has a soft enrage, and if your raid is in this phase too long, you all will get overwhelmed by the increased fire damage stacking debuff.
Zul'jin will do an AoE ability called Flame Whirl about every 15 seconds or so. It is raid-wide and cannot be outranged. First flame whirl deals minor fire damage, but puts a stacking non-dispellable debuff of 50% increase fire damage taken. The debuff stacks up to ten (500%), which becomes almost impossible to top everyone off.
The tank will have Zul'jin facing away from the raid so they won't get hit with Flame Breath.
The raid has to constantly be moving! Zul'jin casts Column of Fire that targets a player and hits that spot for a few seconds. If you stand in it for a full duration, you will most likely die especially when you have a few Flame Whirl debuff on you. Must keep moving!
Use searing totem/ fire elemental during this phase to help the dps. Every little bit of dps counts to kill Zul'jin before the raid wipes from too much fire debuff.
Spread Out!