I agree that the Iron Islands are going to be very relevant to the rest of the series, especially given the cliffhanger at the end. That's why I wouldn't cut them out completely.
But I still think the POVs in Dorne were a mistake. First of all, the # of POVs has kept increasing, going from 8 to 9 to 11 to 12. At some point you're simply spreading the net too wide. In a story of this scale, there are going to be certain events, and often whole series of events and POVs, that happen "off-screen." That's as it is and as it should be. And in the end, though the Dorne chapters weren't bad in themselves and did tell us some new and important things, I don't think there was anything that happened in them that absolutely had to be experienced by the audience first-hand, rather than be explained by another character at a later time. Until book 4, Dorne was an important house whose business took place mostly in the background... and I think that was a good place for it to stay. Besides, keeping them in the background helped give the novels the impression of more depth by the very lack of POVs.
We don't have to agree, but from where I'm sitting Dorne is totally expendable. They're going to have to make cuts somewhere, and that seems like the most logical place to me.