I think the thing that is initially confusing with Harvey is that Dent "dies" as soon as he's burned. Add to that the fact that Gordon "dies" in TDK and yet is still kicking by the end of the film, as well as Maroni surviving quite easily after falling from a similar height, and you have the possibility of ambiguity.
After seeing the film I honestly wasn't sure he was dead. It may have been due to some of these factors combined with the expectation going in that TDK was setting up Two-Face for the next film. Additionally, it was nearly 3am when that scene occurred.
In any case, it definitely makes the most sense for him to be dead, at least thematically. But I understand how many may be confused as to his fate.
After seeing the film I honestly wasn't sure he was dead. It may have been due to some of these factors combined with the expectation going in that TDK was setting up Two-Face for the next film. Additionally, it was nearly 3am when that scene occurred.
In any case, it definitely makes the most sense for him to be dead, at least thematically. But I understand how many may be confused as to his fate.