The Hungering Cold (my new guild) fighting the northrend beats on 25 player normal difficulty.
I added Tirions speech for each part and the intro speech.

In this encounter you fight 3 bosses in a row.

The first is Gormok the Impaler

Now this particularly handsome piece of work is tanked in the middle of the arena by two tanks. Why two tanks? Lets go over his abilities:

* Impale - Inflicts 150% of weapon damage to an enemy and causes it to bleed for 3500 to 4500 damage per application every 2 sec. for 30 sec.

* Staggering Stomp - Deals a staggering stomp that inflicts 9263 to 9737 Physical damage to all enemies within 15 yards and interrupts spellcasting for 8 seconds.


In addition, there's two rather mundane mechanics here. First, people will get periodically attacked by Snobolds. They only go away after being DPSed down by other raid members.

The second mechanic is just plain old patches of fire that spawn randomly - just move out of them.


Second are Acidmaw and Dreadscale

So these are two huge Jormungar worms, much like the one we see in Thorim's arena fighting a bunch of alliance scumbags. At any point in time during the encounter they are both active, with one of them being above the ground and another one half burrowed. Every once in a while they'll both burrow underground completely and come up with the roles reversed.

They are both kept facing away from the raid to prevent frontal cone damage, so lets ignore such abilities for now along with any abilities that deal direct damage to the tank. Lets go over the other ones that deal with the core mechanic of this phase:

Acidmaw:

* Paralytic Bite - Inflicts 12950 to 15050 Nature damage on an enemy and injects them with a paralytic toxin.
* Paralytic Spray - Sprays acid at an enemy and nearby targets, dealing 8325 to 9675 Nature damage and applying a debilitating paralytic toxin.


Dreadscale:

* Burning Bite - Inflicts 11100 to 12900 Fire damage to an enemy and coats them with burning bile.
* Burning Spray - Sprays fluid at an enemy and nearby targets, dealing 8325 to 9675 Fire damage and coating them with burning bile.


As you can see these both deal with two main debuffs: Burning Bile and Paralytic Toxin debuffs.

When a worm is half burrowed it uses the spray ability which puts the debuff on random raid members (and people close to them?). When a worm is above the ground it puts the debuff on its tank using the bite ability. When raid members get either of these debuffs they need to run to each other to neutralize them.

In addition to the above, Acidmaw has a couple of less interesting abilities:

* Sweep - Whirls around, dealing 8325 to 9675 Physical damage to enemies within 15 yards and knocking them back.
* Slime Pool - Inflicts 5088 to 5912 Nature damage to enemy targets within the Poison Cloud.


And lastly comes Icehowl

This guy's encounter starts a few seconds after after the last Jormungar worm dies. It isn't a very complicated fights, so lets go over the boss' abilities:

* Ferocious Butt - Delivers a ferocious headbutt to an enemy, inflicting 69375 to 80625 Physical damage and stunning for 3 sec.
* Arctic Breath - An icy breath that freezes targets in a cone in front of the caster, inflicting 20000 Frost damage over 5 sec.
* Massive Crash - Leaps into the air and crashes down with massive force, dealing 11000 Physical damage to all enemies, stunning them, and knocking them back.
* Whirl - Whirls around, dealing 9250 to 10750 Physical damage to all nearby enemies and knocking them back.
* Frothing Rage - Increases Physical damage and attack speed by 50%.

The tank will grab the guy and drag him to the center of the arena to be tanked there. The raid spreads itself around to minimize the number of people that get hit and paralyzed at the same time by the Arctic Breath attack.

Every once in a while after some tanking and spanking and whirling he'll jump to the center of the arena with a Massive Crash. He'll then turn around facing a certain player, take a few steps back and then do a Ferocious Butt straight at that direction, killing whomever didn't move away.

What can you do though, the big guy isn't very smart and every Ferocious Butt ends with him banging his head against the wall and being stunned for quite a while. We take this chance to DPS him down quietly.

This is more or less about it :)