Yeah, even with perfect wingmen commands and picking subspace jump missiles, it's very inconsistent to win on medium.
You have the two Ravanas to disarm, the ambush squad of Nahemas, the corvette, the cruisers, and the bomber attack.
The Corvette you can destroy almost instantly by killing the reactor. Fine.
The jump missiles are no trebs, and even against the cruisers it takes two double fires to take out one beam, their hitbox is also wacky to hit with your main guns.
Your wing of bombers are terrible at actually killing Shivan warships, their warheads do more damage to you than them it seems.
You can tell your wingmen to guard the keeper, but as they jump from multiple angles, there's no garantee they'll be in position to do much good. If you do it from the start though, you'll almost certainly die from the Nahema ambush, as you'll likely be shredded going for quick kills, they can chase you down (!), or you waste too much time dog fighting them and aren't in a position to disable the cruisers.
In short, it's a very "Ramirez, do EVERYTHING" mission.