Originally Posted by
Razion
Azshara is the most prominently powerful "naturally talented" mage in the setting, and meanwhile Gul'dan is indisputably the most powerful "naturally talented" warlock in the setting.
In terms of power that "any" mage or warlock could possess, they represent the pinnacle of what they can accomplish.
Gul'dan's greatest feat was raising the Tomb of Sargeras.
Azshara's greatest feat was displacing all the water of Zin'Azshari.
(Jaina's flood that threatened Orgrimmar required outside help, if it was stronger so irrelevant as far as feats go to the topic.)
Obviously Zin'Azshari as a zone is a lot larger than the Tomb of the Sargeras on the outside - but on the inside and all the collective landmass it has, the Tomb itself can be quite large. Without pixel measurements of the Tomb to compare to Zin'Azshari, I would tentatively say the zone of Zin'Azshari would be larger and so we can probably tentatively say Mages are more powerful.
Warlock power is quick and easy.
Mages have to study for theirs.
Warlocks can pull from an entire dimension and from endless armies for their power. But this power has never been enough to topple Azeroth. And yet, Malygos in the Eye of Eternity cites its power as being enough to destroy the world ten times over. So, even if we're extending Warlock powers as far as they can go, as far as what has been represented and what is known, while Warlock power is impressive for what you can get immediately the universe seems to kind of indicate perpetually that Mages are stronger when it comes to an average joe who works hard - that the easy path is dangerous, and not worth it, and comes with consequences. Warlocks are almost never the heroes of the story. And by the nature of us, the heroes, and our incessant penchant for victory in the setting, it's no wonder if Warlocks are perpetually portrayed as weaker - that's just their lot that they've thrown themselves in with at least until such a time that Sargeras actually leads the Crusade to put an end to the Void once and for all, anyway.
Edit:
If you're just trying to find the most powerful int based class again, Velen fought off foes that Gul'dan also had trouble with - so considering how we need measurements to determine whether the water displacement of Zin'Azshari by Azshara or the Tomb raising by Gul'dan is greater, we can at the very least know that Velen is stronger than Gul'dan canonically. So, if anything, Priests stronger than Warlocks confirmed basically. And since Mannoroth cites Azshara as being weaker than Archimonde, Kil'Jaeden, and Sargeras, this probably puts Velen ahead of Azshara as well. So Priests, probably stronger than Mages too.