Exactly. It's just a question of who's closer to being eaten. It's in both of their interests to make sure that neither gets taken out. So, if the U.S. is bearing down on North Korea, Iran could stir up some trouble in Iraq and Afghanistan, and bring the focus away from them for a while. Likewise, North Korea has a range of options to get our attention.
We are stuck in Iraq, insofar as we're not free to simply redirect those resources. That means we have a mobility weakness both nations can exploit, to keep us militarily off balance. "Rope a dope" works wonders, and they both are happy to try and pull it off, since both benefit from it.
One factor which can break this game by N. Korea and Iran is Abe's Japan. If Japan comes down real hard on China to pull a plug from N. Korea, N. Korea could die off.
Constitutional revision and rearming of Japan are their aces in the hole. Japan is relatively free from Mid-East situation unlike U.S.
I think Japan's move is as essential as U.S.'s in resolving N. Korea crisis.