The Mages are the biggest threat, don't use paralyze on them as the NPCs will switch off and you want the mage to die fast. Use legsweep near the start of each wave to delay the mage's stacks. If a mage does get a lot of stacks then make sure you are ready to heal their target. Try and paralyze as many of the Mana Stings as you can and if you can't then make sure it hits Jarod and be ready to heal him until the dot is gone. Use Transcendence and Roll to get away from the fixates. You might also need to use Dampen Harm, Fortifying Brew and Life Cocoon to just tank the fixate if you there is a lot of healing needed at the same time. Use lust drums and all the cooldowns you have left on the last wave of adds, once the mage dies it gets a lot easier.
After the adds are dead you can take your time to drink up, as the next stage won't start until you run up to the npcs. You can also wait for cooldowns if you want. When you are ready to continue run into the room where the npcs are waiting.
There will be 6 pulsing eyes around the edge of the room that will slowly move towards you. When they die they will explode for about 2 million damage. The range on their pulse aoe is pretty small so if you stay at max melee range you can hit them without taking damage from it. You can also use Chi Burst and Crackling Jade Lightning if you want to be safe. Heal up quickly after each one dies, as this stage is timed. After the eyes are dead a door to the hallway will open, revealing a Felspite Dominator with 3 bats and Unstable Fel Orbs. The orbs damage and slow you if you are close but if you hit them they go away for a few seconds. Just pull the Dominator and bats out of the hallway and kill the bats first as they get a buff from the dominator. You can use Legsweep and Chi Burst to make it easy. After you kill the Dominator, zap the 2 Fel Orbs with lightning and run past them to unlock the gate to the stairs.
On the stairs there are 4 friendly npcs, and one of them will be running around with a fear debuff that needs to be dispelled. The other 3 npcs have a dot on them and need to be healed to full, as if they die they will turn into an enemy mob and you will have a very hard time beating the timer. Use Life Cocoon on one of them, cast Enveloping Mist on the other 2 and then use Vivify to top them off.
At the top of the stairs is a Risen Arbelest mob. You can paralyze the Mana Sting or use the 3 friendly npcs you healed to soak it for you. Each one can only soak once. You can use a potion of the old war to kill the arbalest faster. After the arbalest is dead you unlock another gate which leads to a stairway full of the fel orbs. Chi burst up the stairway to deactivate all of them and then roll past. After another gate there will be a Dread Corrupter and 3 of the exploding eyes. The Dread Corrupter will summon rotating eye beams that will damage you but he doesn't have much health. After the corrupter is dead carefully finish off the exploding eyes.
You can drink up and wait for cooldowns again if needed before opening the gate to begin the next stage.
The boss in the middle will pull 3 friendly npcs towards him. You need to heal them to full before they reach him. If an add reaches him it will return as an enemy in the next stage. Use Enveloping Mist, Vivify, Life Cocoon, and your artifact ability to top them off. You can also line up chi burst so it hits multiple allies. While you are healing up the npcs being pulled to the boss the npcs in your group will be fighting each other and you need to heal them too, but the priority is on the adds being pulled to the boss. Letting 1 add through can be beneficial since it will make there be a longer rp if you need to drink up.
After a bit of RP, any adds that reached the boss in the previous stage will be summoned and you have to kill them. Deal with them in the same way as the first stage. If you didn't let any adds reach the boss then he will skip this stage and the final boss fight will start right away.
The boss will jump to you, drop a big ground aoe, and he will put the ignite soul debuff from Nightbane on you. The ground effect from the jump doesn't hurt the NPCs so the only damage they will take is from the ignite soul debuff and his melee attacks. Try standing away from the boss and rolling away when he jumps towards you to minimize damage taken. If you are at low health for the ignite soul debuff and you get stuck in the middle of the ground aoe you can die very easily. The ground effect lasts for awhile so try and position it on the edges so you have room to stand. You can use lust drums again here, even if you still have a debuff the npcs will not. If you die don't release as the npcs can still finish off the boss for you.