So fought both the three Wurms and the Marionette. The Marionette seems simple enough, but it requires everyone to be able to play their class well enough to down a champion with random others. The Wurm feels much harder than Tequatl, but we'll see how it pans out over time. So far nobody has downed the Wurms. The closest has been three decapitations.
Marionette:
There are 5 lanes to protect. In each lane, there are barriers and some minor siege to defend with, and hammers to repair the barriers if they take damage. Waves of mobs will come in, but you have to make sure the Watchwork Champs don't make it to the barrier and power-up the Marionnete's cannon. So you clear mobs and focus the Watchwork Champs. Doing this mostly involves slows and snares on the champ, focused DPS, and repairing barriers to continually slow down the waves of mobs.
At intervals, each lane will have the gate open and they can teleport in to where the Marionette is and fight 5 champs protecting the power cells. You must defeat the champ and then destroy the power cell before the timer runs out. When you teleport in, you get assembled into different groups on different platforms. So I don't think there is any way to set up takedown groups. Everyone must know how to properly fight and DPS down the champs. If you succeed then you severe one of the Marionette's strings. If you fail then the Marionette's Cannon gets powered up by like 20-25%.
Once you've severed all strings then I think you defeat the boss. I am not sure as I haven't gotten that far. I do know that the waves and the gates continue until she is defeated or until the cannon powers up. Once the cannon powers up, the giant Marionnette lets loose laser beams all over the zone, killing everyone. Simple enough mechanics. Just about competence and execution.
The Wurms:
There are separate pre-events before the Wurms spawn. These are escort quests where you follow three scientists researching the probes summoning the wurms. You fight a lot of wurms and grubs along the way. Once each escort event finishes, all three wurms pop up in different parts of the zones. So you need to organize across the map. Each wurm has a different mechanic to defeating it.
One wurm involves grabbing explosives from sunken pirate ships and carrying them to the wurm to make it vulnerable. Once enough explosives are taken to the wurm, the DPS phase starts. Meanwhile, tons of wurm husks and mobs spawn according to scale. Also, the explosives are out in the water on floating jetsam. If you drop in the water, you lose the explosive. So you have to jump across floating jetsam and barrels to make it safely to land. So its fighting, running items, and platforming skills.
Second Wurm involves these toxic Abominations. Once one of the toxic Aboms show up, people have to stack on it and kill it, which gives the players stacked in its kill radius a toxic bonus. You then run to a spot on the ground where the Wurm is going to dive down and then rise up to eat you. You get eaten by the Wurm, and then are inside the belly of the Wurm. Once inside the belly, you grab the harpoons inside th belly to break down the outer skin of the belly and weaken the Wurm. You then keep throwing the harpoons at the wurm until it becomes vulnerable. Once vuln, the DPS phase starts. During this time, more Abomination and Champ husks spawn, and wurm eggs spawn, so you need to keep those clear. If there's too many mobs then they'll just kill all the players waiting to be eaten.
Third Wurm is at a research site. You have to run through different colored gasses on the ground and get their buff, then carry the gaseous material to research platforms to fill up their tanks. Once all three tanks are filled with the red, yellow and blue gas toxins, the device will go off and weaken the Wurm. Like the rest, you DPS in this phase.
Once each of these first Wurm phases are completed, the Wurm's head will be decapitated and start running around beneath the ground. It will be invulnerable until all three Wurms are decapitated, and also slowly regen health. I believe if you take too long, the Wurm will regenerate its body. So you have to decapitate all three wurms in roughly the same amount of time. Once all three are decapitated, the Wurm heads will pop out of the ground and start flopping about. They move a ton in this phase and you have 2 minutes to kill all three. Nobody has gotten past this part so far.
So the Wurm fight has a decently long sequence of phases with three separate variations of each phase for each Wurm. It's spread out over the entire zone as well, though the Wurm fights tend to hover around the areas surrounding a body of water.
So far I like the fights. I think the Marionette is simple but fun in mechanics yet more challenging than the regular Zone event bosses that run through the day. The Wurm is pretty difficult on the other hand.