There were other planets on which there were humans before the Shattering, but Yolen had the most sentient life on it of any of them because there are three sentient races there.
Ashyn was destroyed because of their magic users harnessing the Surges (in a different way than with a spren-bond, probably), and subsequently wrecking it pretty entirely. Now, it's not all gone (there is still some life there, with a new magic system involving disease), but it's pretty hard to live there.