What platform did you happen to play the Alpha on? I was playing on XB1 and sometimes the counters worked just fine and other times it seemed impossible to get off no matter how quickly I hit the correct button. If anything it felt like too short of a window, felt like I needed to press it before it even happened.
the problem with it i think is, that on pc it's the middle mouse button pretty easy to get too, but on xbox its the x button, so if you are defending attacks, your thumb is on the right stick, then if they go for a guard break you have to move from the right stick to the X button, and with the current window that can be quite tricky to react to in time. if it was on say LB or click the right stick in, it would be very easy to react too. but then maybe too easy, i don't know.
though that does also bring up an interesting point, for people with elite controllers, they can map the X button to one of the paddles on the back, thus giving them a major advantage over some one using a regular controller.