The whole series is sort of about knights fighting amongst one another, tearing each other to pieces, all the while oblivious to the bigger threat looming (the Walkers in the North).
In books 5 & 6, slowly, we're seeing some of them wake up and get a clue - even though it's still too little, too late, and still being seen through their own eyes and in far too limited a scope.
The Iron Islanders are, in a way, a retelling of a similar story, but one step further down. They're so cosnumed by their own, small and insignificant stories, that they fail to see anything beyond their own borders. We're not talking about the Vikings here - we're talking about, what, ten thousand angry men (and women) who feel they "deserve" to rule because of their ancestors. They are even more self-absorbed, petty and obnoxious than the Lannisters.
They take actions that have far-reaching consequences (sacking of Winterfell, spereading the belief that Bran etc are dead,...) but for all the wrong reasons - ill-considered, ill-informed, practically the sea version of rednecks messing about and annoying the US army in the middle of WWII (I don't mean to imply rednecks were ambushing the US army in 1945 - but if they suddenly did, it would be reckless, annoying and dumb).
That said, I could *easily* see them as the fleet that'll eventually bring Daeny back home. Even though the numbers, as given in the books, would say this is impossible - GRRM has had to fudge numbers quite a few times to make things work.