Malcolm shouldn't have announced who they were voting for.
If Malcolm hadn't announced who they were voting for, they would have had to vote for each other instead of going with their original votes, because they couldn't take the risk it was them.
Now that I think about it, here's Malcolm's best move: "I decided who to vote for tonight by random draw." He would have had a lot more leverage in the next vote if he forced them to pick who to vote out to protect themselves.
It wouldn't have worked. Maybe it would have been a better play, but the outcome would have been the same.
In another forum someone suggested the Three Amigos to not put all votes on Fillup, but something like Phillip 1/Andrea 1/Sherri 1 or so, and then let the 7 fight over it, which would have been amusing, but again, the idols would be gone, and only somehow keeping at least one idol would have been a better success than what happened.
Even Erik figured out they can't let them keep the idols. That 1 in 7 chance would have been worth it to flush out the idols. Like Cochran said, voted almost never change at tribal council, and it was not possible this time either.