It does need to land on her, yes.
I'll throw in some more arguments for Hibiki:
"Sound attacks" is more of a general name for Hibiki finishers because every single attack of his is imbued with purification sound. Technically, his flame attacks can also be called sound attacks.
Rekkaken finishers can create decent-sized
explosions, as seen
in these clips where the fireballs hit the one upfront but affected several around it. So, even if Priscilla dodges the fireball, the explosion may cause her some damage.
Onibi finisher could be useful if Priscilla closes in at Hibiki.
A single glaze could easily set her on fire. Its usefulness depends on how good Priscilla's heat resistance is, but Hibiki's fire can reduce monsters to
ash and completely vaporize them (see above clip), Armed Hibiki's fire should be far superior to that since those feats were demonstrated in his base form.
Given Hibiki's prior knowledge and the fact that he will most likely use ranged attacks in this match, I believe his acrobatic skills will shine. He can
jump several dozen meters in the air and then unleash his wide-area attacks, such as sonic waves or energy slashes. He has previously used
these tactics and is likely to do so again in this scenario.
Lastly, while I know the disk animals won't be exactly helpful as stated above, but I would like to mention that aside from grouping up, they can also be used as
pseudo-
homing projectiles. Again, they aren't a major factor in the fight and are likely to be destroyed early on, but Hibiki will make the most of what he has.
