Well, if you must, I sorta wanted to stop reading after reading about ponies dying and Ponyville being reduced to rumble. I normally don't entertain stories that are more about a character than the story itself, but when I read it, it has some potential.
The first thing you do is make the story as sad as possible by destroying all we know and love about the show by means unknown. On the other hand, it does make me want to find out exactly what happened to cause all of this trouble.
As you have it right now, you don't develop the current setting enough, in my opinion. You could do things like go into further details about how this disaster in Ponyville is being handled, the state of affairs in Canterlot, and perhaps what Dinky has been doing between leaving and arriving back in Ponyville.
Okay, so those are my initial impressions after reading the story. Don't be discouraged by anything I say, I don't mean them in a negative way. Just realize other readers might have similar impressions, so if you see any changes you think would improve the story from what I've said, I encourage you to make them.