I just spotted a problem with the territory arrangement for Karthan: His island has only one neighbouring ocean tile.
Think of it not as a problem, but a solution. Devs meant for you to blockade him and deal with mainland first. Besides, splitting the tile in two won't really "solve" anything - it just means you need to split your fleet and blockade is still in effect. Single ironclad won't stop several transports anyway.
It's a really unsatisfying way to finish the map though, he's stuck on that tiny island with a huge army while you control 99% of the map. You've undoubtedly won at that point and just have to continually stockpile troops till you can overrun him.
