stop moaning as if this is a major issue.
you can't have classes being useless and not being selected for vanilla content. that is just silly argument to want that the same.
keep all the content the same and just introduce balance to the classes which given the years of exp at attempting this, Blizzard should be able to achieve to some extent.
at least enough of a balance that everything can be cleared assuming you know how to play your class/spec and are geared.
very simple solution and not a reason to be screaming the sky is falling.