You are doing the Tal Praiex mission? I don't know how anyone can keep Orioss alive. The Tal Shiar one has you sort of "let" the enemy ships kill him, MUCH easier.
If you are in a middle or late-era game and are lucky enough to be in a Kestral or Hawk ship, you could probably run fast (no cloak) and use the plasma ballet on one enemy ship at a time. Staying at range 15 and skimming 10 to launch plasma is good enough, and if you can get a couple points of reinforcement in the rear shield along with an ECM shift, their weapons shouldn't do much.
You could also suckerpunch the AI. Fire a pseudo S torp, and the AI will probably weasel. If they are CAs and DWs, they probably only have one shuttlebay that will not be reloaded for the full volley of real plasmas that you have.
If you are stuck against a race that is being tough, you could reload the game right before accepting the mission, and see if the mission loads with a different race.
Hopefully the captured base and destroyed enemy ships will balance out the death of the wingman, so you get a draw and are not kicked out of the Tal.