I had a similar thing happen when I did Hydra. A party member DC'd during the loading screen and it pretty much disabled Hydra -- he could not use any special abilities. However, after killing him, the entire party was STUCK in the instance. We could not exit without abandoning the relic quest, which no one would want to do. So we had to sit for almost 20 minutes until time ran out and we did not get credit for the kill.