Does nobody here understand the concept of conditioning?
Yes, the overhead glaive in the Mournful variation is reactable, but if you didn't have that as an option, how would Kitana condition the opponent into going against the idea of blocking low which is usually how players stop Kitana from getting her damage? Having the overhead glaive means that her success rate in connecting throws and forcing you to block Shadow Kicks will increase substantially, and that goes a long way in improving her offense. And let's not forget that EX Air Glaive pops the opponent up for a combo - do you really want to get hit by that?
I abuse something similar with Ninjutsu: once the opponent becomes fully aware of the range I control, if they get too scared to do anything, it opens them up to my run-ins which allow me to start my offense.
As for the poll about the Assassin Strike being an overhead, I stand by what I said here: I'd rather improve its armor than have it be an overhead. I've recently begun experimenting with Assassin for match-ups where having Royal Storm's reflect is meaningless and I like the idea behind it, but the lack of safe set-ups for Sharpen does bother me (outside of using air fan for a hard knockdown that gives you enough time to trigger it), and I'm not sure why a move like Assassin Strike doesn't have enough armor to be used on reaction to those foolish enough to throw projectiles at a bad range.