Zone in is at Toxxulia's Mound.
Once you zone in, for easy mode use your Mystic Channeling Crystal from Tending to Toxicology quest (see related quests above) to get rid of Toxxulia, otherwise she will join the fight when you get to Vuulan.
To begin the encounter, just approach the non-aggro mobs and they will soon attack. The mobs have kickback, mana drain and pretty nasty AOE so it's best to fight them against the wall. It may also be a good idea to position your raid next to the zone in which is where you revive so save on running time.
When you engage the encounter, first you will fight Wyvernlord Tuluun, followed by Wyrmlord Zaos, and then Vuulan and Toxxulia unless you've expelled her. **You can wipe between the mobs and ones you already killed will not reset!**
Tuulan will bring two adds but they are easy to burn and is generally a tank and spank. He has spells that blackout the vision if you don't follow script but I find it quite survivable, especially if you have mana regen. Just keep the group close to healers. If you're blacked out, use your map to get close to the group while blinded.
After you kill Tuulan, Zaos will engage the encounter in about 30 seconds so heal and buff up quickly (he also has two adds which are easy to burn down). Tank Zaos in a corner as he has nasty knockback. Be prepared for emergency heals when he emotes as the tank will be taking massive damage. He will pretty much always keep the tank drained of mana so the tank will just be on auto attack. It's probably a good idea to have a strong auto attacking tank who can generate hate without spells or use hate transfer. It seems Zaos will keep stomping on whoever he's hating so for me it was always the tank.
Finally Vuulan will come and if you have good AOE dps and aggro management the adds are no problem. I found that egg spawned mobs will just go for the tank and a few nukes will take care of them. Over the course of my fight the adds totaled to another 40,000,000 HP on top of mob HP. Overall that encounter seemed much easier than Zaos despite more than double total HP.
(did this with a 95 zerker in tank mode w/ Krivok merc, 95 mystic in heal mode w/ Krivix merc, toons have everage gear and 320aa, 25 prestige aa)