My theory stems from Xarantaur and his Lorehammer.
Story seem to suggest that the Elementals have power granted to them to warp and control time.
Unsurprisingly enough, these Elementals were the Oldgods's generals .
The Bronze dragon flight sent a Dragonsworn (Xarantaur) to handle the problem.
But this whole story line seem to suggest the Old gods have massive power, and are targeting the different dragon flight leaders for some unknown reason.
My speculation (before the oldgod Curse of Flesh retcon in WoTLK)
was that the Dragon Aspect leaders were in some way the Key to the Oldgod's prison. The Titans empowered the Aspect leaders with this power.
The Titans Chained the Oldgods under the planet for a reason. Not because of the Curse of Flesh. But to use them to power the Well of Eternity, as the source of life development.
Each time a Aspect leader is killed, the prison chains for the oldgods grow weaker.
I believed, sooner or later, we would be sent to kill the Dragon Aspect leaders because some of them would be driven mad crazy.
my speculation of cost :
Malygos = Die because he went mad crazy from Magic energy. Linked to the Well of Eternity, which is powered by the Oldgods's energy.
Deathwing = Die because he been driven mad evil by the Oldgods. So we have to kill him.
Nozdormu = Die because we will find out he was corrupted by the oldgods into being crazed leader of the Infinite Dragon Flight.
Ysera = Die, because the Nightmare would corrupt her. Nightmare driven by the Oldgod's influence from their aftermath.
Alexstrasza = Die in combat against Deathwing or some other Corrupted Aspect Leader.
The Halls of Stone computers were """"H,A,C,K,E,D""" by a Oldgod source to give us false information.
Similar to the corruption of the Titan's specialist left on Azeroth to help watch over it.
Proof, of Oldgods influence in Ulduar
"Cough" Yogg-Saron "Cough"
Cool Story Bro