Or even if it happens before NK is a credible nuclear threat, Seoul is in range of thousands of heavy artillery emplacements that'll get at least one shot off.

Or even if it happens before NK is a credible nuclear threat, Seoul is in range of thousands of heavy artillery emplacements that'll get at least one shot off. There's not really a counter to artillery shells like you can use for rockets like the iron dome, so Seoul would be pretty much guaranteed to be leveled, with countless dead.