Blizzard is a private company and has a legal right to impose almost whatever restrictions they want when you use their software and can demand pretty much whatever access they want to your PC as part of their legal ToS.

You don't have to like it just like you don't have to use Blizzard products but you do have to agree to it if you choose to use their products.

Blizzard has for a long time banned 1 action (keystroke/mouse-click) initiating more than 1 action in one or more game clients.

Blizzard has now banned 1 action (keystroke/mouse-click) initiating more than 1 action in more than one game client from at least software multiplexing. If you push hardware multiplexing to play as usual you will likely get our community the clarification none of us want/need (that hardware multiplexing is also banned).

I would try to be creative and work out solutions with no multiplexing... This thread discuss classic classes that may work for the various roles without ANY multiplexing (no hardware nor software) and also mentions at least one retail class (& the ones listed for Classic may work for retail as well).