I don't think it is too late so long as you score high enough to impress adcoms. The way I look at it though is that even if it is "too late" and you don't get accepted because of that fact despite having great scores because you waited longer, at least you got high scores. So even if they did reject you this year, you could still be a shoe in next year if your scores are good enough; something that wouldn't have taken place had you rushed the exam and scored low which would get you rejected both years. I think you're playing it safe by waiting until YOU feel confortable to take the exam. You never know though, you could still be competitive given the late deadlines to so many DS's.