Vashj, final boss of Coilfang reservoir, holding the second of two vials required to access Mount Hyjal, and previously one of the semi-important/major characters of Warcraft 3, similar to Kael’thas.

Abilities

Vashj will utilize a number of abilities throughout phases 1 and 3, phase 2 being relegated to more of a supporting role along with the various adds.

Phase 1 – 3

Melee – Averages 3,000 – 4,000 on plate.
Shoot – Ranged attack, 4,000 – 5,000 damage.

Multishot – Similar the hunter ability, hits targeted player as well as up to 4 others for 6475 – 7525 damage, only used when a target is not in melee range.

Static Charge – Debuff dealing 1619 - 1881 damage per tick to both target and anyone within 5 yards for 15 seconds.

Shock Blast– Deals 8325 – 9675 nature damage to her current target, also stuns for 5 seconds.

Entangle – Randomly targeted root ability, 15 yard range immobilizing for 10 seconds/500 damage per tick.

Phase 2

Forked Lightning – Randomly targeted bolts of lightning, 2,300 – 2,600 nature damage in a frontal cone.

Enchanted Elemental

7,700 HP
Immune to Frost Damage/Snares & Crowd Control
These elementals will slowly approach Vashj, increasing her damage by 5% should they reach her.

Tainted Elemental
These spawn around every 50 seconds, taking the place of an enchanted elemental.

7,700 HP
Immune to Frost damage
Poison Spit – Deals 3,000 nature damage as well as a poison effect dealing 2,000 damage every 2 seconds.
Doesn’t move and will despawn after 15 seconds, also drops the Tainted Core required to deactivate Vashj’s shields.

Coilfang Elite
Spawn every 45 seconds or so at the top of the stairs.

175,000 HP
Melee – around 5,000 on plate

Coilfang Strider

175,000 HP
Melee – 4,500 – 8,000
Mind Blast – 3,000 shadow damage
Panic Aura – Pulsing fear aura triggering every 2 seconds and affecting all within an 8-yard radius.

Phase 1

Phase 1 will be a standard dosage of tank n’ spank fighting, something of a warm-up run for the real fight that’ll start once you begin phase 2 and throughout 3.  Primary objectives would be to remain conservative of mana/cooldowns as well as keeping everyone up.

Shamans can drop a grounding totem to nullify the Shock Blast attack from affecting the tank, this is rather helpful as the boss drops aggro when the tank is stunned by this ability.  Also, blessing of freedom/other root breakers can prevent your tank from being entangled.

Due to Vashj being tauntable an off-tank could be handy for any unforeseen circumstances/the tank is somehow stunned and/or rooted anyway.

Phase 2

Phase 2 begins at 70%, Vashj running to the center of the platform and becoming invulnerable due to a shield.  This is powered by the 4 shield generators that surround the platform and must be deactivated by using the Tainted Core from Tainted elementals on each generator.

During this phase four types of mob will continue to spawn and require management throughout the fight.  Coilfang Elites will be tanked and dropped in stand style, tank grabbing aggro and melee DPS moving in for the kill.

The striders however will be dealt with by primarily DoT’s/ranged kiting due to the ever present fear aura that can be quite disruptive. 
Enchanted Elementals as well as the Tainted Elementals can be dropped by ranged DPS however the Tainted ones will require coordination to handle due to certain circumstances outlined below.

Directly after Phase 2 starts you’ll have a brief lull period in the fighting to prepare for the incoming waves of monster.  Use this to verify positioning and get everyone into working group order before you get hit.

Designating specific areas for each type of monster would be helpful in preventing any confusion on targeting/the who kills what, where type of thing.  Regardless this should be rather easy to pick up, the more important aspect is the Tainted Elementals.

Tainted Elementals

Tainted elementals are on a quick despawn timer and therefore must be handled as quickly as possible, within about 15 seconds time.  Allowing even one to despawn is quite the blow to the raid but more than two practically guarantees a wipe for anything but extremely experienced/geared groups.

Upon killing the Tainted Elemental its core must be looted, this being the item to deactivate the generator, one small quirk though, it paralyzes the holder.  Instead, whoever grabs it must proceed to toss the item, leather ball style, to another player, preferably someone standing by at a generator if possible.

Stationing a player at a generator prior to beginning this process is for the best, setting up a literal chain of players to make certain the process proceeds as smoothly as possible without hindering control of the spawning adds.

Finally, the last generator shouldn’t be deactivated at random, rather making certain it is done so at a time favorable to your current status is best.  Having as few adds up as possible allows you to maximize your ability to handle the newcomer sporebats of phase 3 as well as Vashj and any remaining mobs from phase 2.

Phase 3

Phase 3 is where you gain what is the equivalent of Vashj’s wipe timer, much like other bosses will enrage at a certain state, basically making it a preeminent wipe, the spore bats will prove to be initially a small threat before gradually growing to beyond manageable size.

Have a few players such as hunters, warlocks, mages, etc. dedicated to controlling the spore bat spawn, in general they should prove to be slowly growing in number as you work on Vashj, leading to the eventual overwhelming of those assigned the duty.

At this point if you’re close enough to dropping the boss pull any remaining spore bat slayers back to DPS’ing the boss like mad in an attempt to drop her before you’re wiped by the adds.