When the Titans eventually come, they may not agree with Algalon's assessment. If so, we may find ourselves facing total annihilation. So far we've struggled, successfully, with constructs of the Titans. Loken, Algalon, Archaedas; they've all fallen. But the Titans are likely much more powerful.
There aren't many reference points, but they exist. Sargeras was a Titan and while he has become much more powerful since he betrayed his mission, he is likely still within the same realm of power. The Old Gods were also a common foe, as were their elemental lieutenants. Let's go backwards.
Elementals: We've run into all sorts of these, ranging from small aggressive spirits to the lieutenants Ragnaros and Thunderaan. We defeated them. The Titans did as well. This isn't saying much though since x>a and y>a says nothing of the relationship between x and y. Raganaros was in a weakened state when we fought him though. With the coming of the Cataclysm we'll face him again, likely in his full power, and this will serve as a better measure of our abilities.
Old Gods: We've taken down more than one of these. The Titans killed one and imprisoned the rest, unable or unwilling to kill them. This raises some other questions for another day. In the meantime, we can remember that the Titans could kill Old Gods, they just had reasons not to. Fortunately for us, should we ever come into conflict with the Titans, this means they are not all-powerful. If they were, they could have gotten around whatever was preventing them from destroying the Old Gods permanently. Since we've killed two Old Gods, this would appear to put us at an advantage. However it seems C'thun isn't quite entirely dead. It remains to be seen the full effects and permanence of the defeat of Yogg-Saron. In other words, we again cannot measure ourselves well against the Titans.
Sargeras: Only twice has Azeroth directly confronted him. The most recent event saw him totally defeated by Aegwynn. This is good news. But... She was effectively the focus of magical power, the Guardian of Tirisfal; in other words her power was beyond any we would see now, excluding Rhonin becoming even more god-like for no clear reason or Thrall becoming the new Guardian, which sounds as if it just might happen. The worse part is that Sargeras wasn't interested in winning, he was interested in implanting himself into her son in a dark reflection of the Holy Spirit blessing Mary with Jesus. It was a mere avatar and was possibly weak even by our standards.
The first encounter with Sargeras was when Azshara attempted to summon him. His armies nearly destroyed Azeroth. To give some perspective on his power, a portal was created to let him in, it was this portal's destabilization which created the Maelstrom and fractured the land. That was what was needed to get him in. While the portal was collapsing he was almost able to hold it open. Think about that for a moment: overcoming magical force by sheer strength. The summoning incident was also the only time he was ever wounded: by an axe created by Malfurion and Cenarius and wielded by Broxigar. To put that power into perspective: he single-handedly killed hundreds of demons, making a little hill from which to taunt Sargeras. He was then killed in a single swing.
That we could wound and drive back Sargeras gives me hope. However despite being more powerful, he is still a single being. The Titans are more numerous. We also do not know their method of transportation. Sargeras was able to be beaten because he had to be summoned, making him dependent on weaker minions. The Titans may very well show up instantly and unannounced. Or they may destroy Azeroth from afar. As Algalon was so kind to point out, they are almost unimaginably powerful. We defeated him, but he was a glorified accountant compared to the Titans.
I hate to be a pessimist, but I suspect we're totally screwed. While we might sometimes try to be decent, it should be remembered that most of us are afflicted with the Curse of Flesh: humans, gnomes, dwarves; are space aliens: orcs, draenei; or are horrible mutants with a tendency to summon demons: elves. Who isn't on this list? Only trolls, and the majority of them don't have much of a reputation for not being evil. We killed one of the aspects. And the Prime Designate: "I swear, he was crazy, we had no choice!" And keep breaking into their cities: "But someone else broke in first, so it's okay, right?" And dug up the troggs. Did I mention that we keep summoning demons?
Our only hope lies with the Light. Maybe the Paladins, Blood Knights, and Druids of the Light can surround Azeroth with a gigantic divine shield. And hope none of the Titans trained shattering throw.
Are you prepared? I didn't ask you, Illidan.