My solution:
Have one wing guard Alpha and Gamma each. The Shivans never attack Beta, for me. Ignore the Vasudan freighter, all it does is suck you out of position, and those HoL ships jump out anyway once the freighter escort is gone too. When the "friendly" Vasudans jump in, fire a couple shots at them each, take them to about 30% a piece. As soon as they arrive, c-3-9. The instant they turn hostile, your buddies will open up on them. If they're already at 30 or so percent, they last about two seconds, altogether. Voila, win.
(Played on Very Easy. YMMY)