I am not sure what to think to tell you the truth. At first I thought it could be that Snyder was messing with us, but then the more I thought of it, the more dead Dick Grayson seemed to make sense. We heard rumors of dead Jason Todd (and dead Robin would explain Batman being, as Roven said, "very rough"), but it would be too complicated to introduce two Robins in one single film, so they could have just decided to kill Grayson, the first and only Robin, instead. That is at least what I am inclined to believe right now.