So to summarize the findings in this thread:

5. Each LWH is a separate attack against target

Did I miss anything?

Nope, you are correct.  The LWH missile has one attack, when it hits it does damage as several smaller warheads (number depending on the size of the missile warhead).

It is an easy way to avoid a lot of beam point defense, but it does nothing against missile based point defense.  I am also not sure if it would work in atmosphere.  My gut feeling is that with current rules it would, but it shouldn't work as the atmosphere should reduce the warhead strength.

Brian

I ran a test sequence with laser warheads attacking ships.  The point defense was initially set to 15000 km final fire mode, and no point defense fired.  When I tried normal warheads the point defense did fire but at a shorter range (1000km I think).  I then tried area defense and that did work, but it is not very effective.  the missiles had to be engaged at a long enough range that the fire control had problems hitting the missiles.  The actual chance to hit is dependent on where the missiles end up inside the engagement zone.  For example if the point defense is set to 100,000 km and the missiles end up at 110,000 at the end of a 5 second turn then the point defense will not fire.  If instead the range was 40,000 km then that would be the range the point defense would fire at.  If your point defense beam weapons can fire every 5 seconds, I would recommend setting the range limit to the maximum range of the fire control.  This will give you the most chances of hitting an incoming missile.  Against normal warheads this is problematic as the to hit chances are lower and even if you get a couple of shots fired they may not have as good a chance to hit a missile as in final protective fire.  Against laser warhead missiles, it is the only option available for beam point defense.

Of note is that a CIWS system will not fire on laser warhead missiles at all as they detonate to far away from the ship.

The damage that the laser warhead does is only dependent on the tech of the laser warhead.  Each missile space is considered a different warhead so a size 10 missile with a size 3 laser warhead is treated as 3 separate hits against the armor.  The normal warhead size does not matter for this.

Brian

So what's the range setting for final fire used for? Was that just Steve being lazy with the forms?

It's been a while, but the last time I checked the laser warheads detonated at 10,000 km range.  If you set the range for final protective fire at 20,000 km then it would still get a chance to shoot a laser warhead missile down.  The drawback to this is the point defense will have a reduction in accuracy.  How much of a reduction will depend on the fire control involved.

brian

What if you set the laser to area defense mode or something?

Start a new game (Earth, two players, no NPRs, no spoilers), SM mode, instant yourself a bunch of tech, design a missile with laser warheads, design a missile ship for you and an armoured hulk for the other guy, and shoot a missile.  The give the other guy some point Defense and shoot a few more missiles one at a time.  Design a LWH missile with multiple laser rods. Be sure to SM instant repair the armour between hits, so you can accurately gauge the damage profiles.  Vary the warhead sizes so you can confirm the damage profiles given above.  Report back on your results.

Can someone explain how the actual warhead numbers work? I understand how they fire before making physical contact, and the damage pattern and reduced damage. But to give an example I created a missile that had a WH of 25, when I turned this into a laser warhead the damage dropped to 13 (straight forward I figured simply reduced damage to balance how it skips CIWS). However in the second line I also see "Laser Heads:3", does this mean I get 3 chances to hit, do I do 3 hits of 13 damage each, or something entirely different?

13 damage split between 3 lasers. (2 4 damage, 1 5 damage)

Hmm, I suppose I'll keep it in mind if I run into trouble with missile hit rates. So far, they wouldn't be useful to have.

Basically, it's just a damage tradeoff to be able to ignore an entire layer of point defense. It all depends on how you use it, and how your target is defended. In terms of PvP, I've managed to actually come up with an early game design for a planetary defense network that is almost completely impenetrable to missiles even many tech levels above it, save for either laser warheads or absolutely nutters level of missile saturation (stronger than AMM spam, really). Or 100,000 km/s missiles, but that was still early game tech I was using, so...