I don’t believe that I’ve ever seen a Guidance Scrambler or Missile Revenge Scrambler miss its target. I’ve certainly seen them fail to affect the target, but miss? I don’t think so. I think the main advantage of a Fast Missile over a Multiple Warhead Missile when large numbers of Guidance Scramblers or Revenge Scramblers are present is more that the missile spends less time on the field because it runs out to its maximum fuel range faster, and thus delays the launch of the next missile less than a scrambled Multiple Warhead Missile.
I would tend to agree that Fast Missiles seem to perform better against heavy point defenses than Multiple Warhead Missiles do, but I don’t use the Point Defense Scanner, which says that point defenses mounted on a ship carrying the Point Defense Scanner have a higher chance of targeting live warheads than they have of targeting decoys. If it is the case that this works, then I would expect that Multiple Warhead Missiles would again become a superior option to Fast Missiles, because if point defenses intercept three out of every four warheads deployed by a missile (all the missiles in the game that have decoys do three decoys and a live warhead for a total of four point defense-eligible targets, right?) and the point defenses are more likely to hit live warheads than decoy munitions, then having one weak warhead get through regularly is better than having one strong warhead get through intermittently.
Also, in your computation of the average damage dealt by multiple warhead missiles, you forgot to include one case: that none of the warheads hit. In a point defense-rich environment, it’s entirely within reason that all warheads from any given missile will be intercepted.
So, let’s do an example:
Assuming that we do not have a PD Scanner and point defenses have even chances of intercepting any given warhead in a group of submunitions (3 decoys and a live warhead for FMs, 4 live warheads for MWMs). Let’s next assume that we have one guidance scrambler (GS), and it has a 50% chance of successfully scrambling the missile, and can target three of the four munitions from fast missiles or all four munitions from other missiles, regardless of missile speed, before the missile impacts on the armor or shields of the cruiser (somewhat unreasonable, yes, but we have to make some assumptions). Let us also assume that, were the GS not present, our missiles would always hit (very unreasonable unless we include painters).
- FM - here we have three cases where the GS hits the live warhead and one where it does not. Since our GS is only 50% effective, we have 1.5/4 cases in which the GS successfully defends the cruiser. FMs do 30 damage per successful hit, so average damage is 18.75 (5 out of every eight launches produces a successful hit).
- MWM - here, all four submunitions are hit by the guidance scrambler. We have the following sixteen equally possible cases: all four missiles hit (one chance), all four missiles miss (one chance), three missiles hit (four chances), three missiles miss (four chances), and two missiles hit (six chances). Damage for each of the cases listed is: 44, 0, 33, 11, 22. Average damage is (01+411+622+433+1*44)/16 = 22, which is better than the Fast Missile.
Looking at the cruiser missile comparison thread (viewtopic.php?f=19&t=4646&p=28566), we find that (1) MWMs cannot achieve their maximum theoretical DPS while FMs can, and that (2) MWMs have approximately double the recovery time of FMs. Facts (1) and (2) lead us to the conclusion that, despite MWMs having a higher damage per launch, FMs are more likely to deal a higher damage per second since when a GS succeeds the FMs will launch another missile sooner than MWMs will.
I’m not sure, though, how this ends up applying to the average damage for the MWM - do secondary munitions detonate when any of them hits (which would result in one out of five cases where MWMs take the full recovery time, as compared to three out of eight for FMs), or is it if any of them miss, the MWM needs to spend the full recovery time?