Heroic: Yor'sahj the Unsleeping

Heroic mode (10m, most of it will apply to 25 as well)

Possible Setups: 1 Tank 2 Healers, 1 Tank 3 Healers, 2 Tanks 2 Healers
I'd recommend 1 Tank 2 Healers or 2 Tanks 2 Healers as the third Healer does not really help a lot in the purple phases - and purple will be up in 66.6% (repeating, of course) of the cases.

As already mentioned, there are only six different combinations
Purple, Red, Yellow, Black - Kill Yellow (alternatively, kill purple if you have decent aoe heal cds left)
Blue, Purple, Green, Yellow - Kill Yellow
Blue, Black, Purple, Yellow - Kill Yellow
Green, Red, Blue, Black - Kill Green
Green, Yellow, Black, Red - Kill Green
Purple, Green, Black, Blue - Kill Green or Black

This leads to:
I) healing debuff, stand in melee range, adds
II) Mana Void, healing debuff, don't stand close to each other
III) Mana Void, Adds, more Tank damage plus AoE
IV) Mana Void, stand in melee range, adds
V) stand in melee range, adds, more Tank damage plus AoE
VI) becomes III) or II).

The mana void trick:
If your healers have superior mana regeneration cooldowns, you can choose to let the first Mana Void alive at 20-30% until the second one spawns and kill it right off, regaining your mana a lot faster and sparing one sphere. This is however quite risky at the beginning but pays off later.

Stuff we learned by wiping:
- "V" is the most massive damage phase and a good point for heroism if you don't need it to finish the boss
-Personal CDs matter a lot here, do anything you can to survive, the Healers will always be in stress by mana voids or healing debuffs
- When one-tanking you'll need a CD at the end of every phase (and a strong one for yellow)
- the adds DO have an aggro table, they are just immune to taunts and seem to reset their aggro table again and again. So using misdirect or tricks actually works for a short time.
- the boss does not have a minimum range for hunters, so if there is no green globule, come here and get a hug as well
- always kite the boss to the mana sphere. Green damage does not target melees as long as there are other targets available.
- the Mana Void is targetable and attackable in the air before it draws mana
- no matter what your healers will say in the beginning, purple IS healable, you just have to be on your toes.
- several "additional heals" do not create stacks on purple (e.g. Efflorescene, Word of Glory). Do NOT use Tranquility on purple unless you want to wipe very fast.
- Respec to AoE-heavy specs if you have the option (demonology warlocks, fire mages and combat rogues shine here)

Our learning curve was roughly like this: Wiping on every combination -> nearly wiping on every combination -> wiping on certain colors -> wiping on a certain color -> wiping by "stupid" mistakes -> not wiping.

Have a lot of fun!

About the deep corruption, someone in offical forum wrote this helpful guide

Short guide for 10 mans (how our raid did the 1st kill):

Setup
- 2 Tanks (warrior, druid)
- 2 Healers (shaman, priest)
- 6 DDs (2 hunter, mage, rogue, warlock, priest)

Tactics

• Only the ranged DPS and the free tank nuked the blobs.
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• We always killed yellow when it was up. If it wasn't, then black, which saved dps and group damage at the same time.
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• Green+red doesn't hurt if the whole group positions as closely to the boss as possible while keeping 4 yards of each other (use a range radar). All melee and tank specs can stack on the main tanks' position because neither can be targetted by green. Also assign someone to stand in the center of the hitbox as an orientation point.
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• Dealing with blue: don't kill the first mana orb, only DPS it to about 30%, then leave it. When the next orb spawns, kill the previous one instantly. Repeat.
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• When purple is up, people should use defensive cooldowns. Be aware of what stacks up, and what doesn't, and be careful with things like lightwell.
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• Unless there is green only, the whole raid should position itself in the hitbox of the boss in order to have maximum DPS on the black adds. The hunter's multi shot, which targets the boss, will hit the adds if they stand right in the boss, same with other target-spread AE effects.
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• The boss was taunted at about 3 stacks which made the healer's job considerably easier. The free tank could also try to gain aggro from the black adds.
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Enjoy! :)