NK recently pissed off China, so perhaps something could be worked out in cooperation with them. Artillery remains a problem, but I think that if the attack was swift and accurate enough, it could be taken out before it does too much damage. At this point, I think that tactical nuclear strikes could be a valid option (if it wasn't for political implications, that is).
The problem is that China doesn't want a US-friendly, American troop-filled capitalist nation on its doorstep. They would (perhaps justifiably) consider it a huge risk to national security.
They also don't want nuke-toting psychopaths on their doorstep (they never supported NK's nuclear ambitions). The question is, which one they consider worse. An US-friendly state right by their borders would be a security risk for China, but so would nuke happy NK. So far, NK has been worth the trouble for China, but when it stops to be (and it seems to be going this way), all bets are off.
What would be the purpose of a nuclear strike on North Korea? There's nothing of consequence there that conventional munitions couldn't deal with. And as has been stated repeatedly before, there isn't any sort of preemptive strike on the North that could avoid significant civilian casualties in both the North and South.
The NK artillery batteries are most likely well hidden in forests and would be hard to find and hit with precision-guided munitions. With a tactical nuke, I think it'd be possible to thin them out quickly enough that Seoul isn't too badly hit. Of course, it'd be preferable to take them out with precision weapons, but we're talking howitzers, I don't think that'd be possible. NK most likely has a lot of them, and they're very small and easy to camouflage.
Of course, any attack on NK, especially a nuclear one, would result in massive causalities. The question is, wouldn't refraining from an attack cause even more deaths? Nobody knows how many people starve to death in NK every day, and if the regime collapsed uncontrollably, the final death toll could be higher than even that of a nuclear attack. At this point, I'm afraid that it's a matter of choosing a solution resulting in the least amount of victims.