Or, if she had a self-buff. That would probably move her to top of top tier. If she had a buff that was like Grand Patriot's Elixir, there'd probably be very little competition in boss battles.
I wish she had higher SP, though. Oh, and the best part about MCM? Paralysis ON TOP OF the physical, non-elemental Royal Flare on a fast character. It's not very much, but some is better than none.
Aya is awesome for the 27F so far. 300k Divine Son's Advent against the superfast low-defense things that are weak against wind.

And she can also inflict a good amount of damage against normals too.
EDIT:
Holy crap, I hate the majins and crabs.
Oh well, I think I can take Okuu in my current state. Going to finish exploring 27F then go beat her up.
EDIT EDIT:
Yep. Okuu down. Lost entire front line (except Meiling

) to a fully-charged up Uncontained Nuclear Reaction.
Main sources of damage: HP/ATK Komachi, Nitori, Kanako.
MVPs: Iku, Meiling, Komachi, Rinnosuke
Honorable Mentions: Suwako, Nitori (who survived a Uncontainable Nuclear Reaction!)