Federation Commander

At what point in Defensive Fire are scout sensors used to degrade plasma warhead strength? Before or after phaser fire? If it's before, then that would have a greater effect on the warhead strength than after.

Also, can I use more than one sensor per torpedo? E.g. my base is impacted by a Type-R and it's the only torpedo that will impact before next turn, so I want to use all my sensors on it. If I can, and used four sensors, would the warhead be reduced by 4x25%, or 100%? Or would I calculate the reduction four times each time against a reduced warhead strength?

The rule specifically states that only one sensor may be used against a plasma torpedo. So, in your example, only one special sensor could be used against the Pl-R, for a 25% reduction in warhead strength. No plasma can have more than a 25% reduction due to special sensors.

As for timing, let's just go with the the ESG step in the Defensive Fire phase. (Since their effects are completely independent, it doesn't actually matter whether special sensors or ESGs go first.) In general, Defensive Fire is usually structured to favor the defender, so this makes the most sense.

Any idea why plasma torpedoes loose the built in ECCM that they have in SFB? They are affected by Orion stealth and now only one cheap point of power to reduce them by 25%! Also why is the effect on seeking weapons for scout electronic warfare different than the electronic warfare effects from the Orion stealth?

That is a "Why" question that pretty much has to be answered by Steve.

That said, the ECCM bonus was lost as part of the overall simplification that went into creating Federation Commander. Lots of such little changes happened.

As for Orion stealth, the way it handles seeking weapons has always been unique in FC, and has always operated differently than other EW effects. Don't know why, but it has always been that way in FC.