Well the whispers were trying to correct events to stay in the line with the original story. If anything, the unknown actor suddenly changing events is actually Sephiroth (this new version who suddenly is heavily involved early on, and apparently knows more than he should).
The Whispers being gone has now opened the door for all manner of surprises. Or at least that's how they're selling it.
Whispers being involved in the game as a literal representation of destiny, was just their heavy-handed way of acknowledging the original storyline as still being relevant, while also showing they don't plan to completely follow it.
Well the whispers were trying to correct events to stay in the line with the original story.
It seems to be the case. But a lot about it don't make much sense. The whispers are needlessly introduced in some events when things are changed without any reasons other than to forcefully make them interfere. Why would they need to interfere at first when Cloud meets Aerith? Why wouldn't they have met if they hadn't been there? Why did Cloud try to finish off Reno, when in the original he didn't? Many events are changed first, and then the Whispers interfere. Things don't play out like in the original first, and then they shove the plot ghosts down our throat. Why kill off Barret, just to bring him back minutes after that? What does it achieve from a story-telling point of view? They want us to believe that Barret, having been saved by the Whispers, and the party clearly witnessing this, would go out minutes later to fight against them and get rid of them? How does that make any sense, from a character motivation point of view?
It doesn't. So my guess is that there's more to the Whispers than we and the game's seemingly knowledgeable characters like Red and Aerith are lead to believe. And we'll be fixed on all of this in the sequel.
At first glance, it seems to be a lame meta-commentary gimmick and whathaveyou. But there's so many inconsistencies involving them that I am lead to believe they are not going to be what we're lead to believe so far.