Your tenacity and courage are astounding, priest(ess). You have earned the right to hold the Splinter of Nordrassil. Only one task remains: The Eye of Shadow must be recovered. Scour the world.
The biggest roadblock most will encounter is finding a raid capable of defeating Majordomo. All other steps of the quest can be completed solo or with a few pick-ups.
Getting all possible buffs before accepting this quest will benefit you greatly, as any help from the outside that does not include killing skeletons will help you. Stocking up on potions and elixirs will also help you, as will other consumables such as [Stratholme Holy Water]. Depending on gear and player skill, the quest can even be done purely self-buffed (don't forget Inner Fire).
More important than buffs is the ability to do the required tasks fast. Custom-configuring the user interface can help a lot. In this quest only 4 spells are needed: Abolish Disease, Flash Heal, Renew and Holy Nova. A useful way to configure the action bar would be:
Key 1: Inner Focus
Key 2: Abolish Disease
Key 3: Flash Heal rank 5
Key 4: Renew rank 6
Key 5: Holy Nova rank 3
Key 6: Major Mana Potion
Using the maximum ranks of your spells is not needed as it will get you out of mana pretty fast; the peasants have only around 1500 health, the Flash Heal and Renew used should each heal around half of it.
You should be comfortable with this layout before starting. Practice moving while simultaneously casting Abolish Disease, Renew and Holy Nova.
The "V" key is your friend: it will activate health bars above mobs, making it significantly easier. Unfortunately the bars tend to "jump" around the screen alot. This effect can be minimized by looking directly downwards from far above. Maximizing the "Max Camera Distance" in "Interface Options/Advanced" also helps.
To enable friendly NPC health, you might have to rebind your "v" keys from the Options->Key Bindings control panel. There are 3 separate togglable options that affect this feature. Make sure all 3 are bound to keys (V, Shift-V, Alt-V) and spam all 3 when the fight begins, until you see NPC health bars.
There will be 5 waves of around 10 peasants each, the number will slightly increase from wave to wave. The waves will start at the cave entrance and walk slowly down the road. After the script has started, there will be a dome of light on the road 10-20 yards after Eris. If the peasants reach that spot, they are safe. All the way they will be attacked by Skeleton Archers, they don't do much damage, but enough to kill most of the peasants without healing.
Try to stay cool under pressure, it takes a while, and remember, 14 peasants are allowed to die, that's nearly three per wave. So don't give up early if you make mistakes.
While the peasants move from the cave to the light, you should move with them and perform the following, in order of priority:
Badly diseased (purple): Cure, Flash Heal, Renew
Mildly diseased (green): same as above
below 60% health: Flash Heal, Renew
All others: Renew
Don't take care of any peasants who have moved beyond Eris
The disease kills the peasants very quickly, thus removing it is most important. Next, peasants who are below 60% of their health should get a flash heal, and finally every peasant should have a renew on him by the time he reaches Eris.
It is very important to treat all peasants before they reach Eris. After that, just let them go, Renew will hopefully keep them alive for the rest of the road. Because at that time the next wave will already start, if you don't get back in time, some peasants will surely die from the disease.
If you fail the quest in any way, Eris will despawn and you will not be able to accept the quest for 10 minutes.
Each wave of peasants is accompanied by increasing numbers (from 4 to 10) of Skeleton Warriors. Either gather up many of them and use Holy Nova to finish them off, or use Oil of Immolation. This will kill the skeletons allowing you to basically ignore the skeletons and concentrate on the peasants.
You can bring a friend to aid you. Of course, they cant see peasants without eyes, but they can help other ways, such as giving buffs and providing auras. Be careful: using friends often causes a demon named The Cleaner to spawn. He hits for 4,000-5,000 a swing, immune to all damage and his sole purpose is to prevent people from "cheating", by using other player to help them.