Funny thing is, I actually found the one true use for the Shadow Blade assist, and it’s for playing her on point. It sets her Team Hyper to Shadow Servant instead of Finishing Shower, which makes her THCs activate 8 frames faster, allowing for Hail Storm to OTG after basically any knockdown, including Vector Drain anywhere on the screen. Add to that the decent use as a cross over counter, and it’s not a terrible option.
All of that said, Dark Harmonizer is a stupidly powerful assist on the right team, and with the right strategies in mind. I mean, if you wanted to, it’s possible to use it to play Zero 100% as a zoning character, and beat Taskmaster out in the projectile war. When you combine it with Storm runaway, you very, very quickly create situations where you have nearly 5 meters, and your opponent isn’t even half way to 2, unless they have Dormmamu at least. Purification is about the only thing I’ve found to really give that strategy an issue, as it’s actually hard for Storm to completely avoid them in the air, and it can infinite your assist if you can’t get back down and force him to stop. I honestly think Capcom intended zoning teams to use either Dark Harmonizer or Bloom in this game to actually function entirely as keep away. Even Wesker can make great use of DH though, because it allows you to use considerably more team hypers or Lost in Nightmares than you normally would, and easily allows for every single combo to spend 2 bars on a DHC trick. Not every team needs or can use it, but it is very powerful on teams that do/can.