'who is this woman, and why is she calling herself Delenn?'

Yes, exactly! A lot of the J/D fic I read (which was not an awful lot, so probably I missed out on some good stuff too) just kind of shunted most of her personality into the background. I think characters who are technically the Good Guys run the risk of having anything bad they do excused away, and once you take every part of Delenn that can do bad things, she doesn't end up very recognisable.