Right then, Maddy says I'm on crazy juice but he's just silly. The following theory works, it works I says! *Ahem* Uh right, the actual topic.
I do believe there is more going on with Kairoz on the Timeless Isle than we're told. What peaked my curiosity was when he subtly hinted that the newest vision (the one with Garrosh and Anduin) was indeed part of our timeline. What could this mean? Well, the way my Stargate-infused brain processed it... we are witnessing something pretty big. It may just be that a member of the Bronze Dragonflight has directly begun tampering with the timelines.
I shall specifically point out when a vision deviates from what we perceive as the 'proper' timeline.
Let's start with the first vision. Nothing special there, we simply see how Thrall and Varok Saurfang manage to infiltrate Orgrimmar. This is almost certainly part of our timeline.
The second one shows us that the Klaxxi have joined forces with Garrosh, or appear to have done so at least. Again, nothing special, this is likely part of our timeline.
The third one... ahhh, here it gets interesting. Knowing just what happens in the end cinematics, the positioning of the groups appears odd. Note that Garrosh is lying on the floor, completely motionless. Note how Taran Zhu blocks us from seeing Garrosh's head... could it be that it was crushed by the Doomhammer? As the camera pans out, we see Kairoz overseeing the whole ordeal. Now for the interesting part: I propose that this was what was meant to have happened. I believe this was originally meant to be part of our timeline. Garrosh was supposed to die. Kairoz seems surprised when he learns that he was supposed to be present at this occasion. But was he surprised at being there... or that the hourglass showed him?
The fourth vision shows a destroyed Stormwind and the leaders of both the Rebellion and the Alliance stuck on pikes. This is what happens if Garrosh wins the war. When you return to Kairoz, he comforts you and claims he will continue his research into the possible timeways. This is at first glance not part of our timeline... or is it? More on this in the conclusion.
The fifth vision was the turning point when I began to develop this hypothesis. It shows Anduin visiting an imprisoned orc... and from the NPC ID we know it is meant to be Garrosh. What really surprised me was how Kairoz reacted. He said the prince yet had a part to play... and hinted at this being part of our own timeline. At the same time, he urges the player not to speak of this any more, for fear that they may upset the timeline.
There is a sixth vision as well, for the sake of not spoiling it for people it won't be discussed in this post. However, it would shed some light on the story and I await the quest turn-in text with considerable anticipation.
Now, for the conclusion. What I believe may have happened there. The reasons why Kairoz seems to keep a fair deal of info from us.
Originally, our timeline was to witness the death of Garrosh Hellscream. Let us assume for a moment that he yet has some part to play in the future... and that through his actions, in one way or another, Azeroth is better off than it was (not destroyed perhaps?). Kairoz claims the Timeless Isle is powered by some source not even the Bronze Dragonflight can begin to understand... what if he somehow managed to harness this source and reshape the timeline, poke it and send it spiraling down a different path?
However, he seems a bit shocked at what this meant for Azeroth. It was a worse future, by all accounts. We know from one of the short stories that a victorious Garrosh would mean a shattered Azeroth that cannot stand against the Burning Legion when it returns. So what does Kairoz do? He pokes the timeline again, hoping for a better result...
... and achieving it! Garrosh in this timeline is imprisoned, still alive and, while powerless now, might eventually end up helping after all. Kairoz seems quite satisfied with the result, especially how Anduin is the one to come and speak to the imprisoned orc. What I find intriguing is that while he claims to be an onlooker, he seems oddly secretive and very keen on preserving this particular outcome, going as far as to ask the player to keep their silence regarding what they saw.
This differs from the Bronze Dragonflight's normal agenda in a big way. If he indeed manipulated the timelines, even if his final goal is a greater good, he has stepped over the line.
As a final thought, keep in mind that 'Kairos' was a minor Greek deity, one whose domain was not time itself, but those moments when fate can be changed.