The Joker freaking out about Harley? He should either be in a depression caused by Batman's death or attempting to hunt down Batman's killer. (Who is already dead, obviously, but I doubt the Joker knows the exact details of his death.) When it comes to obsession, Batman trumps Harley any day in his mind.
This does not work. At all. (And that said, I actually really love Dini's work in general and resent the insult against him. He can be an excellent writer when writing Batman, Zatanna, the DCAU, etc.)