I believe Meagon is correct, Silan corpses disappear much quicker than mainland. Most likely so the group can respawn quicker so more players can get a turn at them for quests/grinding. But seeing as this isn't really a problem anymore with the smaller population, maybe they could fix it to make it less frustrating for new players.
On the mainland you can wipe out a whole spawn before the corpses disappear.
On the mainland you can wipe out a whole spawn before the corpses disappear.