Also, I think it's pretty clear that Joker didn't want to kill the Bat family...this latest scheme was a "love letter" to Batman regarding their relationship, as Snyder himself put it a few months back. A message. He is always attempting to find new ways of unhinging Bruce...this was just the latest. Bruce also turned his game right back at him with the threat of revealing Joker's identity to him as well. It's all psychological ploys with Joker, that yes on occasion sometimes get taken over the edge, but I don't think that was the intended case this time.