You mention one HY-2 was diverted by chaff, so Aegis missed it? That's a pretty impressive feat for such big, slow, old missile.
There were no AEGIS vessels in the vicinity. The Missouri's only escort hat day was the HMS Gloucester, a British Type 42 DDG, which shot down the other missiles launched with two Sea Dart SAMs.
You can try IR but you'll also need to take out every chicken hauling Dong Feng truck. The Serbs barely got scratched during Operation Allied Force.
It's a total war situation, so I doubt it would be much of an issue.
I'm not sure I buy that mobile launchers are somehow less survivable than static guns. The armoured casemates is no match for FAE or a 1,000lb bomb 20m away.
The only armor consists of the frontal plates, if the casemate has one. They are generally protected by anywhere from 10 to over 30 feet of steel reinforced concrete overhead, with thick walls in the various rooms to limit damage. Above the ceiling is a much thicker layer of earth, and near the top, burried about 3 feet below the top, there is a concrete burster course, which is designed to prematurely set the delay fuse on an armor piercing bomb or projectile, causing it to detonate before it hits the concrete, or before it can penetrate it. They are generally well-protected and have performed well in combat. A mobile missile launcher, once targeted, has absolutely no protection.