Those islands are fine for island hopping navigation. You can take example from the Pacific. Islands from New Zealand to Hawaii were known and populated from the stone age. They could be known by sailors for ages, hence no effort to "discover", but unpopulated, hence, still a ground for colonization racing.

I've got to ask, though. That large sea between Swefendlea and Ascanta - wouldn't it be where largest trading coastal cities would develop? You have lots of distant territories connected by sea-way, I imagine large ports and carthage-genoa-venice-like states developing in there.