They’re working on a reaction system which, from a game developer standpoint isn’t easy to implement in a meaningful and enjoyable way for players. At a basic level you’d have every enemy attack paused to give you the chance to react. The best implementation I can think of is to que a reaction so that it activates if the trigger is executed. Which is a whole mess of programming to do.
A kind of reaction-que is already there from the start. You can put a few things on reaction and whatever would get the proper trigger first will be executed. Many players didn't like it for the lack of control. Plus in D&D you can transfer all your actions into a reaction as in "I'll wait till that guy will go to our wizard and then I'll rage and smack him hard". And that's something I personally still would love to see at least in form of postponed turn.
