The reason for shield mitigation is to reduce the benefit of focus-firing, and not because it represents some sort of "physics theory" of how shields work in Sins. Consider - five frigates versus five 2000-hitpoint targets, each shot does 100 damage. (These numbers are made up, and healing is not included in the description)

1) No shield mitigation at all:
Case 1: five frigates all fire at the same target first. First salvo does 500 points, second does 500 points, third does, and so does the fourth. Target dies after 4 shots, and it takes 20 shots to kill them all.
Case 2: five frigates fire at separate targets. First salvo does 100 points against each target; still takes 20 shots to kill them all.

2) Shield mitigation starts at 15% and goes up to 65% after lots of damage.
Case 1: five frigates all fire at the same target first. First salvo does 425 points (500 less 75 points of mitigation), but target is now at 65% mitigation because it took a hard hit. Next shot against that target only does 205 (500 less 295 points of mitigation), and it takes 9 shots to kill each target, or 45 shots altogether.
Case 2: five frigates fire at separate targets. First salvo does 85 points against each, but mitigation only partially kicks in because damage per target is pretty low, and sinks back to 15% by the time the attacker's cannon warms up and fires again. So second salvo does 85, third does 85, and so on. It only takes 13 shots to kill all 5 targets.

So in this extreme and made-up example, by not focus-firing and scattering their firing across all viable targets, the player kills the enemy fleet almost four times as fast. Of course, these fake numbers don't cover effects of autohealing or power-ups, but the theory is sound at least.

It was an attempt by IronClad to reduce micromanagement so players wouldn't have to constantly monitor battles and select-their-fleet-then-select-one-target over and over. It *does* help a little in evening out the auto-target-selection process that an automated AI uses when two enemy fleets approach each other, but focus firing is still an advantage.

-- Retro

hm but focus fireing is good so that you can quickly take out 1 target asap so that it doesn't retourn fire...

 That's the essential thing;)

 and the way you mentioned it there's a good chance your own ships could be knocked down...

As to focus fire vs diffuse fire;

 

If you focus on one enemy at a time, you'll give them the maximum shield mitigation bonus, so your effective damage will be lower.  However, once that target is destroyed, its is no longer capable of using special abilities or causing damage, hence your fleet will no longer be threatened by it.  It's a trade-off; you can focus fire if you really want to remove a specific enemy from play, or you can just use diffuse fire to maximize your general damage output.  Focus fire makes most sense for strike craft, since kiting (running the unit that's being focus fired away so that its attackers have to chase it) is not viable against them.

 

Typically, shield mitigation also benefits smaller armies, since the fewer relative units you have, the higher you can expect your average shield mitigation to be.  This means that, where 10 units might otherwise steamroll 5, those five units can not only hold out for a long period, but also cause more damage than they otherwise might have without shield mitigation.  You can try it out; send three unupgraded cobalts to an asteroid defended by an enemy cobalt and siege frigate.  By the time you kill the cobalt (siege frigate is almost negligable), one of your cobalts will be half destroyed.  In other words, for every point of damage your three cobalts dealt, that cobalt did approximately two thirds of the damage, even though it actually had one third of the fighting force.  Its effective damage output relative to your's was doubled thanks to shield mitigation!

 

There are 2 mechanics at work here...

1.  A shield at high charge is energy inefficient, and while it protects you better from its reserves, it does it inefficiently and loses energy faster.  At no standing charge, the shield is still up and doing a lot to ablate total damage, but unfortunately can not stop all of the energy so hull damage starts to occur

2.  The more force or energy trying to penetrate a shield, the less can actually make it through, probably do to careful tuning from the engineers on board the ship to the type of weapon being used against the ship.

 

You don't have to change your tactics much, focus fire is still tremendously powerful.  It doesn't take much to knock a ship up to full mitigation, so most ships you fight will be at higher mitigation anyhow.  Better to just focus fire and get them dead. 

The main thing you want to avoid if you can is "overkill" with missile ships, where you accidentally force them to fire more missiles when they want to change targets because the missiles in the air are sufficient to kill the old target.  When I am fully micro'ing a battle, I often switch MOST of my missile ships to a new target when the last one is near destruction -- just leave a couple on the old target to change at their own discretion.

This is one of the main reasons why you don't want all 100 of your LRM's on the same target.  Unless that target is a Progen. 

From what I've seen, armor is effectively a 5% health bonus for each point.

 

Dude if you spilt all your fire between all enemy frigates you will lose 100% of the time. Once you reach the shield hull boundary, the hull regen combined with shield regen will pretty much cancel 50% of your damage. So your mitigation will be pretty much close to what it would be if you focus fired them 1 at a time, in theory anyway.

Well his example did assume equal force.  In a case of 4vs2 that would only benefit you vs AI or Militia. As any player worth his salt would retreat.

From the maunal:  "Shield Mitigation-  This a special trait which all shields share due to the nature of how the protective barrier is formed. As a shield is assaulted, computer systems automatically adjust its harmonics to match that of the incoming weapons fire.  This has the effect of completely negating a certain percentage of the enemy weapons attack.  Once the primary shield has failed, emergency generators are brought online to maintain this last line of defense throughout the armor of the hull."

That's why focus firing large groups on caps is still the most effective way to kill them.

 

Heh, wait 'til late game when your caps last maybe five seconds apiece.

 

Yes Woca, faced with even 20 LRFs, ur cap will be done in.  Imagine losing a cap ship to fighter squads, fighters not bombers, before you can move your cap ship from the planet you were bombing to the edge fo the grav well to jump.  Then you will know the true pain of capship survival.