But the point is there's not enough evidence to suggest it was intended as an homage to that particular movie, because that particular movie's Joker death scene was not unique enough to rule out a coincidental similarity.
Good point. If the Joker's death in the 1989 flick had been more unusual--like, say, being buried to death under a mountain of bat-guano or dying of an overdose of laughing gas, then we could probably assume it was a deliberate homage if something similar befell the Joker in TDK.
But falling from a building? Not so much.