This may turn out to be a bit rambly, because it touches on a large number of topics, but I'd love to get some lore junkies to weigh in here.
We've got a lot of villains, and a lot of allies out there currently. For villains, at the top of our adversary list are the Burning Legion and the Old Gods. At the top of our allies list are the Naaru, and (presumably) the Titans. I'm curious how they all fit together.
Of course, there are the Old Gods. Most sources say that they arrived on Azeroth after its creation. Their whispers were behind the madness of Deathwing. Their death rattles spawn Sha, making victory over them also eventually end in defeat. They are chaos itself, and are the mortal enemies of the Titans (who value Order above all).
Then there is the Burning Legion. The Burning Legion is led by Sargeras, a Titan who was tasked with enforcing order by eliminating chaotic races like the Nathrezim. Faced with the chaos of the universe, Sargeras despaired and fell to Darkness - enslaving these races into the Burning Legion. He as sent his legion on a Burning Crusade, a quest to bring destruction to all worlds that were ordered by the Titans.
Seemingly unconnected, right? I think, however, that if you look deeper there is a connection. So far as we know, the Old Gods pre-date the Burning Legion, or at least their presence on Azeroth pre-dates them, by countless millenia. If you think back to the Burning Legion and what brought them to Azeroth, you'll remember that it was the War of the Ancients, when Azshara attempted to summon Sargeras into Azeroth. This led to the Sundering. You'll also remember that it was during this time that Deathwing, already influenced by the Old God N'zoth, began creating the Dragon Soul/Demon Soul - supposedly to combat the Burning Legion, but in actuality meant for it to enslave the other dragonflights (Keep in mind that the Dragonflights are led by the aspects, who are empowered directly by the Titans).
Could it be that N'zoth, and not Sargeras, was whispering to Azshara as well as Deathwing? Could the Old Gods be in league with the Legion, or simply using the Legion as a tool to bring chaos to Azeroth?
Let's look at another, more concrete example. The Infinite Dragonflight's actions during BC and Wrath indicate that they are working for the Burning Legion - every one of their plots, had they been succesful, would have led to the victory of the Burning Legion. Had Arthas never purged Stratholme, he never would have become the Lich King and wrested away from the Legion, allowing the Legion to use the Scourge to destroy Azeroth. Had Thrall never escaped Durnholde, the Horde would never have left for Kalimdor, and Kalimdor would have falled under the might of the Legion. Had they succeeded in stopping Medivh from summoning the Horde to Azeroth via the Dark Portal, the Eastern Kingdoms would have been soft due to years of peace, and would have fallen quickly to the might of the Legion. But wait! In End time, we see the true endgame of the Infinite Dragonflight - and it coincides with Deathwing's ultimate plan, the Hour of Twilight - Which is orchestrated by the Old Gods!
So... build me the connection, because I see bits but not the whole picture. How are the Old Gods and the Legion connected? I don't buy it that they are completely seperate - at the very least they are using eachother to further their own goals.