Hmm just deleted a char on my account and it worked fine - less than 1 second after I clicked ok - is this a heroic one?
That's about the only thing I can think of is if its one of the original (2014) heroic that were given out and if you try to delete one of those you get a warning message. The other heroics (paid or bought and most recent given out in 2017) can be remade with no issue. So if it is one of those there could be a server issue that is not sending you the warning message and as your not getting it you cannot do the second confirmation so it all just stagnates. Guess if you really need to delete the poor guy then file a petition or just wait and try again in a month or so.
Maybe there is some popup that says are you sure or something and it is off the screen? I had that happen before with changing resolutions around.