I regularly do on a tac captain in a moderately outfitted Guramba (MK XI gear, borg 2 piece). I full impulse past the group till sitting next to the middle nav beacon and line up with the middle freighter. Once they at about 5km, I open up with an ability buffed CSV3 and if I am placed just right can disable all three with one volley. Even if I do not get all 3 it usually does not take long to get them blue, and then looted. I usually do not aggro the first fed ship. I wait here for the next trio, and disable them. By this time I am usually under fire from the second ship, and take it out fairly quickly and am able to snag the optional.
I have also done this with a similar tactic with my engi in her Tor'kaht as I often forget it CAN cloak .
The freighter assault is cake. You don't need cloak. Simply full impulse AROUND the first group, and come in BEHIND the far trio of freighters. Then throttle down to half engine power and hammer them all on their aft shields. Ignore the enemy ship warping in, and continue to pound the back 3 freighters through their front shields. Do not beam over ANY cargo, just disable freighters. Once you've got all six freighters disabled, kill the reinforcements. At this point you might have some of the first ships you crippled be repaired enough to get under way again, BUT they don't have any shields. Simply zap them til they stop, then collect your cargo all in one go, taking care not to accidentally warp out after looting freighter number 3.
Do the freighter assault like I suggest and you can't fail it. The pitifully weak reinforcements are not dangerous enough to kill a player-controlled warship. Your worst worry is accidentally destroying a freighter that you've burned too much with a warp core breach. If you lose one that way, you're okay, if you lose two, you fail the mission.
Probably the harder way to do it than many have suggested but always seemed to work for me is I just simply burn all of the freighters till they stop then kill the defenders.
If one of them repairs and decides to move again just attack it till it stops again. I know its probably not the easiest or most efficient way but thats what I learned on my own and seems to work fine.