The Brits lost Sheffield through a comedy of errors. The missile warhead was a dud, but a fire was started from residual fuel. The missile severed the ship's fire main, so no pressure was available to fight the fires. Four nearby ships contributed a highly touted portable fire pump, but all of these failed, leading to an investigation by the RN afterward. Some glaring construction defects in the superstructure meant the crew could not set fire boundries, and she lost internal communication. USS Stark a few years later ate two Exocet, one of which exploded and the other a dud, but the crew fought the fires and brought their ship home. A missile hit is not a slam dunk kill. These were both 4200 ton ships, but Sheffield was all steel in construction ( I'v stuck a magnet to her sister's superstructure so it is assuredly all steel ) while Stark had aluminum upper works.
ECM. Jamming is far more sophisticated than simply flooding the environment with energy to be overcome. Most jamming takes advantage of the characteristics of the system being jammed to create false echos. Combine the false echo with chaff and flares that are deployed into the same point in space as the false echo and one creates a very realistic target for the incoming missile, diverting it from it's intended target. Read up on techniques such as inverse gain jamming, range gate stealing, crosseye and buddy to get the feel for this art. Larger platforms are much more successful at jamming because they have the electrical power to create a false echo that is stronger than the actual echo, a crucial necessity for most jamming to work. Sometimes however, it can be something as simple as firing the CIWS to flood an enemy radar with false echos ( a technique used to fool the radars on TU-95's ).
The MARV'ed IRBM's I'm aware of used their maneuverability to achieve smaller CEP's. As the missile falls towards the target, something like a Pershing would use an active radar to find it's target and then maneuver to hit it. These were fixed targets however. No one has demonstrated a MARV than can track a moving target like a ship, and as the missile falls, the area over which it can successfully maneuver shrinks quite rapidly. It would have to find the target at it's apogee or very close to it to have enough maneuver space to catch a fast moving ship. Not impossible, but not the slam dunk often implied. Btw, a carrier strike group under a weather system with it's radars and radios off is essentially invisible. This is a technique the US Navy uses all the time to hide carriers from prying eyes, or to achieve surprise. Read up on how Admiral Ace Lyons snuck a carrier strike group into the Barents without the Soviets finding it.
Missiles in combat. Take a look at the Israeli experience in the 1973 war. There were two major surface engagements between Israeli missile craft and Eqyptian and Syrian missile craft. Something like 48 missiles were fired at the Israeli craft in these two engagements without a single hit. All were spoofed by ECM. The Israeli's sank all of their opponent's craft, and keep in mind he Styx missiles used had a greater range than the Israeli's Gabriel I's, giving the Eqyptians and Syrians the first shot advantage. In Operation Praying Mantis, the Iranians shot multiple supersonic Standard missiles at the US Navy at close range, and all of these were successfully spoofed by ECM. CIWS was never used. Do not underestimate ECM, it has a great history of success.