Karen is even worse of a nightmare for Night March than Lysandre's Trumph Card. All the Battle Compressors, Ultra Balls and Trainers' Mail would stay behind. But this counter is so incredible specific I'm not sure if I feel comfortable putting it in my decklists :/
Considering how dominant NM and Vespiquen decks are, I think it's worth having at least one in your deck.
Karen I have mixed feelings on. I feel that is too hard a counter for Night March and related decks. I've never been a fan of such hard counters without some kind of cost. I'm glad it exist because I hate Night March but this is another example of bad card design.
The Night March player can't do anything about this card being played against them and no one deserves to lose to a single card drop, no matter how toxic the deck is.
I think it's a case of "lesser of two evils": it's not the ideal, but NM got way too dominant in the metagame. It was already very good, then it got even better with Puzzle of Time.
For most people the best solution would be ban Battle Compressor, but I don't like this idea either; it would affect lots of decks, especially Fire, Dark and the ones with Archie/Maxie engines. I don't think that would be fair.