haha! I was waiting for a thread like this to pop up.
I play the PC version of the game but I use a 360 controller, but I think I can see your problem.
Your keyboard does not support the ability to register the inputs you need for DT at the same time. All keyboards are different, for example I can press QWER at the same time and it all registers, however if I press RT, I am unable to press any other button on my keyboard at the same time.
The fact that they don't allow you to bind DT to another key is ridiculous, especially seeing as I don't use the Y button for anything on my controller.