As one of the "ganging up" members I'd like to make several points clear:
Dark Onyx betrayed the Empire and made numerous Sith angry IC. The repercussions for angering one of the two Galactic hegemons are now catching up with him. When you anger a superpower, it tends to go overkill. See USA drone strikes.
Darren Shaw, instead of helping to capture the traitor, is assisting his escape. Ashin declared him a traitor as well. I don't see it as ganging up on when an Empire makes its top priority the elimination of a high valued target. This is realistic story wise. Completely realistic. You betray us, we annihilate you.
So here's the deal, if you want to betray and flaunt an entire faction there are consequences. You don't get off scott free. You aren't a karma houdini. These consequences are now being exacted. Yes, you are being ganged up on, but not because people feel spiteful. It's because Onyx betrayed the Empire and now he is getting his just rewards. Bottomline, the Empire brought firepower to the table that neither of you were prepared for. The trap was set, sprung, and now you and Onyx are caught in the middle of it. Now deal with it. Or beg for the Empress' forgiveness.