I have to admit its been a while since I played ACTA (I still play FC every week though).
With plasma in ACTA I always found that there was one tactic basically - charge and get in whilst you have overwhelming firepower. Don't try and get clever with long range manouvering/cloaking. Use the terrain (there should be some) as much as possible to mitigate long range shooting. Once you are close nothing can withstand the sheer damage output of plasma armed fleets on a point for point basis.
There was some worry about klingon front shields, but it may be worth looking at it from another angle.
A klingon D7 being attacked through his front shield can take ~36 on the shield (probably a bit either way depending on rounding and volley size etc) and another 22 in hull hits. So it takes about 58 raw damage to kill a D7. A Fed CA takes 56 to kill as I remember, a Gorn about the same. The klink is not much stronger up front compared to other cruisers, he is just a lot weaker outside the front.
The Romulan equalivalent to the D7 is a KE. That takes 30 shield and 12 hull, the Rom is armored so will usually shrug off an extra couple of hits, needing more like 14 hull to kill, a total 44 hits. The larger klingon hull means it is more likely the devastating crits from plasma will contribute a bit of damage to killing it, so in practise you will not need to hit the klink with 58 damage, but maybe only 53. So there is only about a 10 point or less difference between the Rom and Klink even through the klinks front.
What can each ship do attacking wise? Ignoring special actions, but assuming range 8 (for P1 killzone and plasma optimal range) the D7 can bring 7 phasers for ~9 and 4 disrupters for ~6 and 2 drones for ~7 = ~22 damage. The KE can bring ~8 from phasers and ~39 from plasma = ~47.
Ignoring counter measures, in a single turn the Rom does twice as much more damage to the D7 than the D7 does to it, the Rom will have scored hull hits and possible devastating crits whereas the D7 is relying on luck to get an odd leaker. Over 2 turns the KE scores about 55 damage to the 44 from the klingon. So both have a good chance of killing each other in two turns of shooting.
Defensive fire can clearly make a big difference. If both sides do all the defensive fire they need to (or can rake up) you see the Rom give up 2 P1s to stop ~2D6 and the Klink give up 7 phasers to stop ~5 or 6D6. In such a case the Rom inflicts ~23 and the Klink ~6.
Big edge to the Rom in one turn, but over 2 turns, the KE is doing about 27 and the Klink about 21. Neither side is through the shield yet even after 2 turns of shooting (barring leakers).
This is a fleet game, so with say 5 D7s vs 5 KEs you are looking at the klingons dishing out ~100 and the Roms ~225 if they all go full offense. If the Roms put 2 KEs on one D7 then the D7 will not have those phasers to fire at the second lot of plasma. Two KEs should kill a D7 with noticeable overkill. Two D7s, however, will not kill a KE unless the one being plasma'd forgoes any defensive fire, then they can just about take out a KE - but that just means a D7 dies with less firepower at him and the rest goes onto the 2nd D7. There is a fair chance that 5 KEs can kill 3 D7s in one go even if they go defensive. If they do not go defensive you might kill 4 D7s in one go. The D7s struggle to compete with that.
Where the Roms struggle is of they lose a ship or two before getting to fire properly, or they fire outside range 8. Plasma in ACTA is not game where you dribble it in. Plasma is easy to defend against, but only up to a certain point. Every point over that threshold makes plasma increasingly potent, every point below it and plasma is increasingly weaker than simply losing a dice. If you fire at range 8 (in the above fleet) you may only be adding 15AD or about 37% extra dice compared to range 12, but that will increase the amount of plasma damage that gets through a defensive klingon by maybe 50%.
There are of course other factors that change things. The Klingons can overload, though that can be hard to pull off with more than a couple of ships (6" move and 6" range). Shield boost helps the Klinks if they are hit in the front, but the D7s can only throw 1D6 (other ships are better of course). The KEs can throw 3D6 shield boost which is pretty impressive, especially on subsequent turns when you are trying to repair shields. The klinks weapons may roll lots of 6s and ignore shields. Some klinks may well get caught out side Front shield arc and die really fast. However, SAs don't really alter the basic maths - the disparity in raw firepower at close range makes klingon front shields not that much of an issue, at the end of the day the amount of damage to kill a klingon cruiser is not much different to any other cruiser.
The point is that plasma is a very hard to system to balance given how it works. The klinks have to play well and to their strengths to beat someone who will wipe them in a simple shootout.
PS when I played the Roms in ACTA the KE was my workhorse ship, that is why I was using it in the above comparisons (and the D7 for the same points). It may be ultra fragile on the inside, but 30 shields, armored, command and very good plasma payload per point spent.
As for the question of playtesting.. it's clear there wasn't close to enough of that.. so saying that something is invalid because it's already been tried is a bit moot - the current system doesn't work.
That comes down to what you mean by 'works'.
If you mean plays/feels just like SFB/FC then no. If you mean that klingons will have to use agility,drones, long range disrupters and avoid showing their rear. Whilst the Roms have to try and get into poistion to make a useful 'launch' then yes it works. That is what both sides are trying to do in ACTA and it is what they would probably be doing in SFB/FC, each game just represents it in a different way.
I personally am not keen in ACTA any more, plasma and drones feel wrong - but to be clear plasma is damn potent as it currently stands, hence if you are going to win you are likely winning big but if you are going to lose you are probably wondering how you are meant to win, the mechanics can't really leave much room for anything in between (and is often the case in any game with a super potent side/unit that has to be beaten by not letting it get its super shot off in the first place). I also feel ACTA is a bit to random, too much too often comes down to a couple of 50/50 dice rolls, and they are often ones revolving around defending against seekers (Evasive or IDF) as it happens.