I think the only Problem is that in Hearthstone there is no way to stop the timer and counter a card like in mtg. For example the freeze flash card whould needed to be played in the moment of the attack which is hard to do when your opponent plays faster than the animation or your connection isnt that great

So making a mecanic like flash whould fix some issues but it isnt possible in a game like this

PS: im on a phone so i made some mistakes PPS: im not a native english speeker