The Three did their thing about 100 years before game.
The Muud'ari ship had to be thousands of years before that time. The Forshaken are an off-shoot of the ship crash, which had to have time to spread throughout the area, and eventually try the failed gate that destroyed the empire.
Per in-game text (?), humans were send ahead of the ship to spread out as a slave population ready for use when the ship got there. (Someone double check me there.)