Oh heck! That's the one bad thing about the patch. Instead of facing a balanced Hydran ship, you get all those INS and their fighters. I could never do that mission. Usually, I just forfeit that mission or run off the border, and then get zero prestige points. Fortunately, it's not like SFC1 when you fail a mission, you don't get "kicked out" of being a pirate.
If you really wanted to beat the mission, maybe you could load your game whenever that mission shows up. Then, you could play different missions and build up your fleet. When you finally were strong enough, you could try the mission. My fear is, however, that if you go in with a bigger ship, there may be even more H-INS+, like 10 of them.
I would also like to know how on Earth someone would win this mission.