Aya almost always gets two turns with that skill because Aya is too fast.
After she uses her first turn, she can refill her timebar fast enough so that she can act again before anyone else.
It doesn't matter whether the skill sets her timebar to 20000, 10001, or even 99999.
For example, with a Lv. 100 Chen and a Lv. 8 Aya, Chen will get a turn before Aya's second if Aya used something like Focus on her first turn.
And again, that confuses me, because if a skill is going to push up the time bar like that, then why 20000? It really is confusing that they don't simply make it so that the spells and other actions of all the characters simply subtract from the timebar. I mean, the Shock status ailment(halves timebar), Yuyuko's spells, and the Diva subclass are all proof that the game can do that, so why is everything else set like it is?
And it's not like every single skill should be useful to everyone who has it.
Sungho, I'll presume that you did not mean Suwako's "Native God of Earth" skill, because if you did, I would flat out say it: If a character has a skill that isn't useful to them, then why do they have it? I would kind of understand if it was something simple and plain like Agility(more about that below), but a character with a skill that allows for a complete recovery of HP should have a situation where she can use it, especially if the name of the skill is thematically appropriate for the character.
Also, I just realized that Suwako and Kanako both have enough room for two more skills,, so I'll say what's on my mind and think of what could fit there...
Suwako: Seeing as Agility is probably there as a thing to keep Suwako from being slowed down by enemies, and Suwako is not someone who can benefit from this unless she's hit by something, I see it as a sign that you're supposed to swap her out if she takes any damage at all, so that she doesn't take two hits on the field. That said, I'll leave Agility alone, and just advise that Guts and Beat Down be added to her skill set. The former is as I said before, to make a skill combo with her unique skill "Native God of Earth", and the latter is mainly for when you use her multi-target spells to deal with floor trash, so that she doesn't run dry on MP so quickly while you go exploring.
Kanako: Ah yes, the other goddess of Moriya Shrine. I have looked into her skill set, and I can easily recommend two things to aid her further: Encounter with a Formidable Foe, and To Increase One's Fighting Spirit. The former aids Kanako in boss battles, where this skill, plus the Majesty skill, will really help in ramping up Kanako's stats in a fight. The latter is in tune with her durability, as it grants her more offensive and defensive power with each passing turn. Of course, were her "Ability to Create Heaven" skill able to reduce damage taken as well as it's normal effect of increasing damage dealt, she would become almost unstoppable... (Would she be OP if it was all added up together like that? If so, then I would have to recommend something else, but what?)
And that is all that I have for now.