Is your party also decked out in PvP gear? That would be a huge problem. I would imagine you have stats that are useless help against hardmode bosses.
Champion Gear is easily enough for Black Talon Boarding Party and Foundry. Easily killed all but the Boarding Party last boss because it's ridiculous and Foundry last boss because someone misplaced a decimal point. All without enraging. Haven't done the others.