I feel like there should be a quest on "paper tanking" to prepare all Dps/healers for the inevitable moment in which they are forced to do it lol.
In cases like this, though, I usually try to, very politely, inform the tank that they are making mistakes. If the tank communicates, then I will continue to provide feedback for them as we go. If the tank blatantly ignores the chat box and continues to run amok, then it's fair game, as far as I'm concerned. I inform the healer (unless I am the healer) to prepare for some paper tanking.
