I don't think that's what they meant by being forced.
In 3.0, I stopped playing WHM in raids because it felt like I was purposely handicapping my party. AST could (and still can) do everything I could do, but offer more. So why am I playing WHM? That's the feeling you have when the power gap is so huge as it is now.
No one's going to be forced into different roles, but you'll feel so weak and unwanted that you will eventually fall into something you don't have as much fun playing.