[dkw]

The poor "balance" with the various scenarios is to show "real world" situations. Unfortunately, Harpoon is a VERY DETAIL oriented game with EXCESSIVE Micro-Managing of EVERYTHING. Missing one little detail can doom you to failure, and I have failed far more often then I have succeeded, average win/loss ratio (by my estimation for myself) 1 win for every 30 losses.

Sacrificing a weak ship to survive is a good tactic, and it is what many real world people would do in your situation. Think of it like chess, sacrificing a pawn to remove your opponent's rook.

You also need to pay very close attention to all the details of every little thing. Moving ships around in their formations, direction of facing, use of radar and sonar (who, where, etc.), how to use and combat sonar in regards to a thermocline, the difference between a HARM, AMRAM, LR load out for your planes and helicopters; the list goes on.
Don't forget that "Narrowing your Profile" (turning into or away from the attack) reduces the chance your ships will be hit. That tactic works better against torpedoes then missiles, but the computer uses that tactic regularly even against missiles so it has to be worth something.
Going along with the "Narrowing your Profile" is "Weaving." By "Weaving" aka Zig Zaging back and forth, it constantly causes the enemy missiles to keep changing directions, which helps evade enemy missiles as they are more likely to over correct, fall short, over shoot, or run out of fuel because they are no longer going in a straight line to get to the target.
Don't forget how Radar works; sends out a wave of radiation which bounces off things and comes back to the sender. Out in the middle of the oceans and seas, you are the only thing out there. However, if you are close to land, the Radar radiation bouncing off the land can help hide your ships, buying you a few extra seconds at best.
Sonar works similarly to Radar, but uses Sound under water. At a certain depth, there is a natural phenomenon called a thermocline. Sonar coming down from above bounces off that and returns to the ship, while sonar coming from below goes right through. You can hide submarines under the thermocline, making airborne and surface sonar unable to locate them.

There are all sorts of little details like that in Harpoon that can cause you to lose.

In the Norway scenario that is being discussed, occasionally, one of my Destroyers was armed with a couple short range SAMs, which managed to shoot down 2 enemy missiles. That helped my ships live long enough to actually launch all 6 Exocets.
Don't forget, your Destroyers have a 40mm Air Defense gun on their Stern, but it can only fire at things directly behind your ships. During my attempts at that scenario, that 40mm actually shot down a missile and bought my ship enough time to fire off another salvo of Exocets before being destroyed.

Players also have to learn HOW the A.I. reacts to situations. The A.I. likes to launch attacks at Maximum and Near Maximum ranges, but this varies. If you can turn your ships fast enough to run away from the attacks, sometimes the enemy missiles fall short.

Truth be told, I am no where near as skilled as my father was at the game. He could get a Decisive Victory on any scenario no matter which side he played. He was a master of strategy games; beat Harpoon, 5-Star General games, Red Storm Rising, Steel Panthers series all with Decisive Victories in every scenario and/or campaign, to name a few.
Most of my advice for Harpoon comes from what I learned from him.

Scenarios where you get Aircraft Carriers are MUCH easier once you learn how to use a carrier's planes.

Harpoon is unforgiving, just like real war. The original developer of Harpoon wrote books for NATO about Ships, Planes, Subs, Ship Based Weapons, and techniques for combating them. Many times as I read through the manuel and tactics guide it keeps saying, "You need to learn for yourself," "Learn from your mistakes," "Get the experience needed to win through trial and error."
Harpoon is all about Details, Knowledge, Experience, Initiative, Instinctual Decision Making, and Speed. You don't have time to sit and wait for the right opportunity; you have to make the opportunity appear.