I don't buy the echo theory because, as far as we've seen, you can only use it once at a time. By that I mean, while you are using echo you cannot currently use echo again to go further back. There is no precedent for a multi-level echo existing. Thus we cannot already be using echo as we use it in the current story. Plus it would be pretty lazy and kind of a cop-out. If they were really going to use an echo theory, why even go along with this whole Dalamud bit? Just say, well it was all an echo from a long time ago, the landscape has changed since.

Honestly that theory, if it was right, would kill any motivation I actually have to try and do the events to "stop" Dalamud. I mean if we're using echo then the events set in motion will happen no matter what, we cannot change them. Hate fate, it denies free will.

I'm still going with the, we destroy Dalamud but pieces of it still rain down upon Eorzea which changes the landscape, theory.