... that without some manner of standards, anything can be justified 'indirectly'. For example, you say that Rand forcing peace between the Seanchan and the rest of the world, leading to the Aiel being bored, leading to the Aiel waging a war against the Seanchan they cannot win, leading to their destruction as a people after thousands of years, is sufficient justification for attributing the destruction of the Aiel to Rand.

I say it is not. These are not Prophecies of things that will happen, they are specifically prophecies about what Rand will do, and I require a more direct connection between Rand's actions and the end result.

It also sort of misses the point of the prophecy. In Aviendha's vision, the Aiel cause their own destruction because they were bored. They are a people for whom survival has always been a struggle and war has always been a fact of life. Now they are united, no longer fighting with other clans, and living in peace on lands that are, to them, excessively abundant. The problems of Aviendha's vision are thus these:

1- The Aiel have no purpose beyond fighting.
2- The Aiel are too numerous.

That second problem is the important one here. It is actually the inverse of the Rhuidean prophecy, which states that Rand will destroy the Aiel except for a remnant of a remnant which he shall save. Aviendha's vision contains instead a future where the Aiel destroy themselves because Rand saved more than a remnant.