the point of the game is to have the player make a decision between taking cards in his deck or not.
Not to have the player pick cards that he clearly must take and that every1 good also takes, and have some cards that clearly nobody with a brain will ever take, which result in people having a bunch of the same cards in their decks
I think even with tower -2, some players will still take the card, and some won't. so its a good choice.
the reason why i think its still good is:
the card reduce ur tower by 2 BUT
reduce ennemy wall by 1, and a ressource by 1
so the effect is a little bad for you, but keep in mind its increasing your ratio of uncommons (you get less commons in a way)