I'm not an expert on this, but, those numbers don't seem awful to me. I realize not everyone started the game at the exact same time, but retaining 75% of your users a month later seems pretty good. Pretty much any mobile game is going to have some churn, and given their stratospheric launch it's not like they were realistically going to grow. Given the (MAJOR!) quality problems they've had, they can probably stem the bleeding quite a bit if they just fix those things.