Some Ricardo vs Mia Analysis
Fated Day's End does the equivalent of 31 Lunar Damage to Mia (After considering her Mdef and Fire halving). This means it 7HKOs. I'm not considering recharge times except for doubles. This balances out because recharge times=lower damage average anyways, and I believe Ricardo did have some magic damage with no recahrge time.
Mia has to halve Wind for her to have any chance, since Ricardo does have some Wind magic that will likely 5HKO her at worst otherwise, making their absolutely no way for her to win under any argument I think. I assumed she did.
Wind Cane Mia does 28.2% to Ricardo, and I assumed 118.4% speed. Mia definetely needs the Wind Cane, because otherwise Ricardo is getting in a free shot of his 5HKO physical, and he'll be like 20% naturally faster, and getting a lot of doubles with Gale. If any of the elemental resists are tied to the Dragon Rod (Wind or Fire resists that is), then she'll lose no matter what staff she equips. She effectively does 18.2% to him a turn with Regen in, and then he can go and heal another 35% (Basically two of her turns after Regen is factored in) and he'll get doubles, so if he 5HKOs her, it's an easy smashing.
Mia 1: Ice Shell
Ricardo 1: Arc Gale (Just for really killing the sake of Mia’s doubles, He’s at 140% speed about for 5 turns, but this has a little lag this turn I think. We’ll say the lag pushes makes his speed equal to hers this turn. This lasts until his 6th turn)
Mia 2: Attack (Ricardo takes 29.2%)
Ricardo 2: Fated End’s Day (Hit 1) (Ric at 19.2%)
Ricardo 3: Fated End’s Day (Hit 2) (Ric at 9.2%) (Normal speed surpassing since Ricardo is about 20% faster. If you see Mia at as higher SD, this will still happen, just later on.)
Mia 3: Attack (Ricardo at 37.4%)
Ricardo 4: Fated End’s Day (Hit 3) (Ric at 27.4%)
Mia 4: Attack (Ricardo at 55.6)
Ricardo 5: Fated End’s Day (Hit 4) (Ric at 45.6%)
Mia 5: Attack (Ricardo at 73.8)
Ricardo 6: Arc Gale (Ricardo at 63.8)
Mia 6: Attack (Ricardo at 92)
Ricardo 7: Heal (Ricardo at 48)- Just for fun, I’m not going to assume Ricardo doubles Mia ever. This is balance out people who might see her at a higher speed, and still have him win.
Mia 7: Attack (Ricardo at 76.2)
Ricardo 8: Fated End’s Day (Hit 5) (Ricardo at 66.2)
Mia 8: Attack (Ricardo at 94.4)
Ricardo 9: Double Attack: Fated Day's End+Any Other of His Spells. Hits 6 and 7, Mia is dead.
So yeah, Ricardo does it within his SP alloted time, and and even recharge time likely couldn't change this enough to have an effect considering that he still would have 6-7 more turns.