#1 Ouro - 87 days from the Twin Emperors' death. 26th April 2006.
#2 C'thun - 86 days from the Twin Emperors' death. 25th April 2006.
#3 tied Chromaggus - 74 days from Ebonroc's death. 25th September 2005.
#3 tied Ragnaros - 74 days from Majordomo Executus' death. 25th April 2005.
#5 Yogg-Saron, Alone in the Darkness - 70 days from Stars' first pull. 7th July 2009
#6 High Astromancer Solarian - 59 days from Magtheridon's death (unlocking the Eye). 24th April 2007
#7 The Four Horsemen - 56 days from Gothik's death to D&T's kill. August 25th 2006
#8 Al'ar <Phoenix God> - 48 days from Magtheridon's death. 13th April 2007
#9 The Lich King (Heroic 25) - 42 Days from Heroic Putricide's death (first pull). March 26th 2010
#10 Heroic Al'Akir 25 - 36 days from Heroic Conclave of Wind's death. January 22nd 2011.
#11 Kael'thas Sunstrider <Lord of the Blood Elves> - 31 days from Solarian's death (first pull). 25th May 2007
#12 Magtheridon - 29 days from the first level 70 25-man raid. 24th February 2007
#13 Lady Vashj <Coilfang Matron> - 17 days from being unlocked. 29th March 2007
#14 Leotheras the Blind - 16 days from Hydross' death. 4th March 2007
#15 Loatheb - 14 days from Heigan's death. 17th July 2006
#16 tied Heigan the Unclean - 13 days from Noth the Plaguebringer's death. 3rd July 2006
#16 tied Hydross the Unstable <Duke of Currents> - 13 days from Gruul's death (Unlocking Serpentshrine). 16th February 2007
#16 tied Heroic Cho'gall - 13 days from Heroic Ascendant Council's death. 15th January 2011.
#16 tied Heroic Nefarian - 13 days from Heroic Atramedes' death. January 9th 2011.
#20 tied Archimonde <The Defiler> - 10 days from Azgalor's death. 9th June 2007
#20 tied Gothik the Harvester - 10 days from Instructor Razuvious' death. 30th June 2006
#22 tied Mimiron Firefighter 25 - 8 days from Ensidia's first pull. May 1st 2009
#22 tied Sapphiron - 8 days from Four Horsemen dying. 2nd September 2006
#22 tied Gruul the Dragonkiller - 8 days from Maulgar's death. 3rd February 2007
#25 Reliquary of Lost Souls - 6 days from Gurtogg's death. 2nd June 2007
#26 tied Kel'Thuzad - 5 days from Sapphiron's death. 7th September 2006
#26 tied Kil'jaeden <The Deceiver> - 5 days from the opening of the third Sunwell gate. 25th May 2008
#26 tied Sinestra - 5 days from Heroic Cho'gall's death. January 20th 2011.
#29 tied Heroic Anub'arak 25 - 4 days from Heroic Twin Val'kyr's death. September 6th 2009.
#29 tied M'uru. 4 days from the opening of the second Sunwell gate. 4th May 2008