No. It doesn't. Perhaps you should carefully look at what Chronicle actually says before throwing out "literally" and quotation marks. Chronicle made it very clear that the damaging part was
HOW the titans killed Y'Shaarj. Aman'Thul reached down and ripped it out of the ground. Such a forceful action tore open a massive wound in the world where Azeroth's arcane lifeblood bled out.
Aman'Thul himself reached down through Azeroth's stormy skies and took hold of Y'Shaarj's writhing body. With a heave of his mighty arm, he tore the Old God from the crust of the world. In that moment, Y'Shaarj's gargantuan bulk was ripped apart. The immensity of the Old God's death rattle shattered mountaintops and obliterated hundreds of titan-forged where they stood.
Y'Shaarj was dead, but its tendrils had bore more deeply through Azeroth than Aman'Thul had ever imagined. In excising the Old God from the world, he had inadvertently ripped an eternal wound in Azeroth's surface. Volatile arcane energies—the lifeblood of the nascent titan—erupted from the scar and roiled out across the world.
Horrified by this turn of events, the Pantheon realized they could not risk killing the other Old Gods in such a manner. The malignant creatures had embedded themselves so deep into the world that tearing them out would destroy Azeroth itself.
--Chronicle
Just killing them in place would have nothing near as damaging an effect. Yes, the OGs will corrupt the land around them when they die as Yogg states, but this is not the same as ripping a huge chunk out of Azeroth.
C'Thun was fully awake and free.
Originally Posted by Blizzard Entertainment
Worse, C'Thun has awakened, freed itself, and reemerged from the planet's depths. (
WC Encyclopedia)
We did kill C'Thun. This is stated in the quest,
"Even in death you can feel the legacy of C'Thun's evil around you." and in the comics. The plot of the comics was Cho'gall trying to resurrect it.
Yogg had broken through all but the last of its restraints.
Originally Posted by Blizzard Entertainment
This ancient horror has corrupted its guards, and now it is breaking through the last of its restraints. Faced with the peril of Yogg-Saron's imminent freedom, a band of mortals has made preparations for a sweeping assault on the city. (
Game Guide)
We killed Yogg as well. Yogg says it's gonna die and is salty about it.
"Your fate is sealed. The end of days is finally upon you and ALL who inhabit this miserable little seedling. The shadow of my corpse will choke this land for all eternity."