Always leave 1 f type in the tube. That way if he does run up you can pound him with KZ phasers of you're own and then launch a F to eat up his Gatling which is 1 weapon system so even if it only did 2ad to a torpedo it would still have used all four to shoot it down.
If he has run up to you (by which I assume you mean gatling killzone) why would he use a gatling, when he could use the 2 ph1s. The gatling is far more useful shooting you and the Ph1s are more likely to kill the Pl-F without overkill.
Given that you kept a pl-F back presumebly means that yuo did not have as much punch with your main Plasma launch. All you are doing is swapping 2AD in turn 1 for 2AD in turn 2, at best you are merely delaying 2AD damage you could already have done, at worst you are not doing 2AD damage that you could have done by overloading his defenses in the main launch.
Wanting to use phasers and a single PlF also means that your ability to engage in Power drains becomes a lot more resrtricted (all you can do is take the 6" move option). Being move limited is bad, if you have launched in the previous turn (as it sounds like you probably are talking about) then you are already fairly close, and don't want him going past you where you struggle to turn to face.
If you are already close then you may find that he can get out of the arc of the Pl-F and you won't get to use it.
I was thinking about the Gorn vs escort matchup last night/this morning. In the context of what Matthew said about replicating results of FC/SFB, I double checked his statement, and it was indeed 2 ships meeting up that should produce similar results (rather than 2 fleets meeting up, which might make more sense for this game). I'm not sure about SFB, but in FC a Gorn BC vs a Fed CLE is going to be a win every time for the Gorn. It can ripple the plasma over the turns forcing the escort to run or use gatlings defending itself. The Fed drones are not a great issue for the gorn, drones being readily avoided in FC. That leaves the Gorn with a phaser advantage, better shields and more bulk. The escort is not going to win that in a month of sundays, it might take quite a few turns but the Gorn will wear down the escort.
In ACTA, however, I couldn't see how to get that end result of winning all the time (or at least close to). I shuffled around counters trying to work it out. The escort is in for a hard fight, but so is the Gorn. If the escort goes head to head then he takes the plasma strike at some point, he will hurt a lot if the Gorn has moved last and avoided the gatling centerline. What hurts the Gorn in that matchup from my play around is that turn mode 6" makes it hard to stop the escort skirting around and getting to a point that the Gorn can't keep his plasma bearing, especially with terrain lying around. Once he is in that position then the Gorns only real possibility appeared to be risking the HET, but that only works if he moves last (first and the escort just goes back past him). If he doesn't HET then with phasers getting diverted to anti-drone duty he will get outshot (and he will if he doesn't shoot drones). If he fails the HET he suffers even worse. It is still far from a clear escort victory, as always in ACTA the randomness of a couple of 50/50 rolls will have a large effect, and terrain may also have quite an effect. However, it seemed like the escort actually had a half decent chance. That sounds OK until you realise that it neither replicates the result it is supposed to, and more importantly, within the context of ACTA itself, one ship is almost half the cost of the other.