Well, this question has been up for years and I've been thinking for this for years aswell,
But reading about Destiny's Edge what they've been up to before PC became a hero, they've been fighting against Kralkatorrik once Before and his minions, loosing Snaff and Glint, fighting against Destroyers, the Guild disbanded, and also fighting in Jade Sea!
So DE has actually been in Cantha?! Why are there not more information about this? They've been fighting at the Jade Sea so that means they've been in Cantha, even though they kicked out and banned all non-human creatures and closed it's border, though this was before Zhaitan was awaken… so that's probably why.