With cards like Swamp Hag and Haunted Woods the only way to know you're going to be attacked is to look at the log. There should be some notification on screen that there's something going to happen on your turn due to a decision you'd make normally. Especially considering you may have had a long action chain anyways and have to scroll up in the log to check if they have any duration attacks out. This could be as simple as showing the opponent's duration cards in their play area.