If you can’t stand the heat get out of the kitchen
Have you had your first Supremus encounter? Was it your last? Supremus is the second boss of the Black Temple and can be defeated. That is he can be defeated if you develop the winning strategy. One way to do it is to repeatedly trying different approaches and watching your character and others die in the process. Another way is to read the supremus guide at www.worldofstrats.com. One you have read the guide you will realize that Supremus is really quite vulnerable and that all you have to be able to do to defeat him is heal your tanks and withstand heat.