So I have actually found a very detailed guide about this encounter. Its pretty long so I've took some of the basics add pasted them here for an easier read.
Its a great guide, If you get chance. Pass it on!
Event starts here. http://quagganspress.files.wordpress.com/2014/01/w0.jpg
When it starts you are required to defend 3 vigil commanders that split up into 3 paths and head to each of the 3 wurms.http://quagganspress.files.wordpress.com/2014/01/wmap1.jpg
Blue - Cobalt Wurm
Red - Crimson Wurm
Orange - Amber Wurm
You will have 15 minutes to kill all of the wurm’s heads, or else the event will fail.
If you manage to kill your group’s wurm-head before another groups, the timer will be set to one minute. This means you must coordinate the kills of each wurm-head to be within 60 seconds of one another.
If you eat the nutrients that lay on the ground, then the wurm-head’s spit will not to hit you. If it were to hit you otherwise, you would lose your phytotoxin buff, “wurm attraction” buff, or bomb that you are carrying.
Always try to have the nutrient buff.
If you do not fell like getting involved in the tactics of the encounter but want to be there for experience. Then the best thing you can do is run around and kill Eggs. On all 3 wurm encounter, eggs spawn. If you kill the eggs before it hatches. No mobs appear. Worth!
The boss spawns with an invulnerable shield. To remove the shield you need to set off 20 explosive barrels at roughly the same time.
There's 2 spawn points for the barrels clearly indicated on the map.http://quagganspress.files.wordpress.com/2014/01/w10.jpg
You need 20 people to pick up a barrel and make it to the wurm without touching the water or being hit by an AOE circle. The barrels need to be place in a organised location.
Once the shield is down, tbh i have no idea if it comes back up. Not seen that far.
Fairly simple. You get buffs from running inside a cloud. You run the buff back to a corresponding zone.
Red cloud - Red Zone
Blue cloud - Blue zone
Yellow Cloud - Yellow Zone
Requires 20 people to fill each zone. 5% per person. You start on the zone and wait for your debuff to disappear.
Once all zones are filled the extractor will start and remove the shield from the wurm.
If your not buff running then you should be killing mobs/Eggs.
The idea of this one if to stand as close as possible to the mobs with the yellow buff on their heads. http://quagganspress.files.wordpress.com/2014/01/w12.jpg
When they die you will get the buff. Once 20 people have it. You stand on the red arrow infront of the boss and the boss will eat you. Once inside, you must kill the sphincter of the wurm until you are spit out.
Once you are spat out each person remove 1 stack of vulnerability, 20 people removes the 20 stacks and you can begin DPS.