I had a thought the other day regarding the balance between fedeation and klingons ships in PvP.
Now, let me begin by saying that I generaly think that the two factions are balanced on paper. Each side has advantages and disadvantages, and all and all I think that player skill is the deciding factor in most PvP matches.
However I realised that there is one difference that may make klingon PuG teams more effectibve than their Federation counterpats. Since all klingon ships can mount dual cannons, and use CRF to apmlify that advantage whereas only select federation ships have that capability I think that focus fire from a klingon fleet of random composition has an advantage over focus fire from a federation fleet of random composition.
For example, a fleet of 3 escorts, a science ship and a cruiser, will do way more damage than a fleet of three science ships, a cruiser and an escort, but a fleet of 3 BoP, a raptor and a battle cruiser is much more comperable with regards to damage potential to a fleet composed of 3 battle cruisers, a BoP, and a raptor.
This could explain some of the perception that Klingons are overpowered.
In short, the difference between Klingons and feds in PvP is due primarily to skill and a slightly more forgiving learning curve on the klingon side makes Klingon PuG teams more "skilled" than their Fed counterparts because it takes less optimization at the team level to get the full potential from their ship.