For those thinking of trying for the Faceless One title before the pre-patch, which requires soloing both Horrific Visions with all five masks active, below are some general tips on how I did it. It has gotten a lot easier now with better gear and overall familiarity so I can sometimes go for extra objectives during 5-masks but if you're trying it for the first time I advise doing only what is needed to finish the run. If anyone has any questions about specific areas let me know.
The most important resource in a 5-mask is time (vis-a-vis Sanity). With that in mind:
1. Crystals and chests are not worth it.
2. None of the buff mobs in either instance are worth it. Seriously. The buffs sound good on paper but waste precious time to get.
3. Potions are useful if they are convenient but only go out of your way for the +100 sanity potion.
4. Don't try for the Mail Muncher if your goal is the title.
5. Buffs: Ghastly Goulash, flask, augment rune. Heroism on Shaw and Alleria in SW, and on Thrall in Org. Some people like to Hero on Rexxar too but I do him last so I must save it for Thrall.
6. Bring some K'Babs too. These have a three minute cooldown so be careful that you will out of combat long enough (10 seconds) to get the sanity before you eat one.
7. Try very hard to have at least one orb left for the end boss. They will smoke you if you pull with low Sanity, especially Alleria.
8. SW order: Dwarven District (Therum Deepforge), Old Town (Matthias Shaw), Trade District (Slavemaster Ul'Rok), Mage Quarter (Magister Ulric). Run in that order and the only portal you will need back to the Cathedral is after Mage Quarter. You'll be ignoring the mobs in the back of the Square.
9. Org order: Valley of Wisdom (Vez'okk the Lightless), Valley of Spirits (Oblivion Elemental), The Drag (Inquisitor Gnshal), Valley of Honor (Rexxar). Again, if you run in that order you will only need to use the totem after Rexxar to get back to the Valley of Strength. You'll be ignoring the mobs along the right side of the Valley of Strength. You could do Spirits before Wisdom if you want but I think the other way is less running and therefore faster. YMMV.