Feds do benefit from larger fights.
Take the extreme - 1 vs 1 in a klink vs Fed game. The Feds lose out on 2 fronts.
First, there is the problem of keeping the agile klingon in arc, with only 1 ship to worry about the manouverble klingon easily keeps out of the front arc of the Fed, or at the very least least can easily keep his front shield facing the one ship.
Second, probabilities don't favor the Feds photons, a ship with 4 photons may never see the much needed 6s rolled. With the lower number of rolls that he will be making, the deviation from the average is that much higher, yes he has a better chance of the spectacular roll, but he has the higher chance of the awful roll, and even his average is not favourable given that he already fighting the manouvering issue - a single leak is not likely to be that bad.
Take the other extreme - say a 20 vs 20 fight.
First, With so many Fed ships it is now harder to keep klingon ships out of the front arc of all fed ships, anywhere you go there likely to be some Feds ship waiting. Even when you are in the front arc of Feds it is a lot harder to keep every one in the klingon front arc. Relatively the klingons manouvering edge has diminished.
Second, With a lot more photons to roll for the deviation is a lot lower, you are far less likely to roll all hits or all misses. Not only that but even the average is now very significant, at 5 photon leaks you are odds on to kill a D5W just from those leaks. In a 20 vs 20 fight with say 60 photons you are likely to be pretty close to 10 leaks per full volley, enough to have decent chance to kill 2 D5Ws just on photon leaks (or one C8).
Disrupters are nice weapons, but 60 disrupters won't kill anything of consequence via leaks, they will not even likely cripple an enemy cruiser purely on leaks, so they have to go through shields to get the job done. That makes the disrupter a very different weapon. Sure they do a lot more damage over 2 turns, but they have to do that much more damage to get the same job done.