Okay, stream of consciousness (kinda) about the Clarissa/Arnaud match.
Clarissa's optimum strategy actually isn't just Rob Turn->Sac->Sac, but to use Rob Turn until she has three upcoming turns, Howling Shot to safely attack (it can miss, but can't be reflected). Howling Shot + full-HP Sacrifice kills Arnaud very, very easily, seeing as a single Sacrifice does 97% to Arnaud. His HP isn't that above average.
So, we basically have a situation like this:
If Clarissa has one upcoming turn:
75% chance of this becoming 2
25% of Clarissa "losing"
If she has two upcoming turns:
75% chance of this becoming 3
25% chance of this becoming 1
If she has three:
31% chance of Clarissa advancing to the stage where she can win with one more Sacrifice.
69% of dropping to two turns
Sacrifice: 75% chance to win on first hit, 25% chance to "lose"
I know there's a way to calculate situations like this but I forget how. Anyway, if you just consider the simplest outcomes from using a max of 3 Rob Turns, then using Howling Shot if she has three turns, or just two Sacrifices if she doesn't (or if the first HS misses), then she has a 45.4% chance of winning. I suspect the actual odds are higher but I can't prove it, and I'm not confident they're over 50% at all. However!
I put "lose" in quotation marks because in all cases Clarissa does have a chance to come back, it's just not very good. Having the first Sacrifice reflected lowers her HP to the point where her offence really sucks, so I'll assume she always loses there. However, giving Arnaud a turn is less instantly fatal. His best strategy seems to be to use Slow Down and then Blast her once (assuming an instant double), and hope for luck with Rob Turn missing from there.
Now, if the first Rob Turn misses, we get
Rob Turn (miss) -> Slow Down -> Blast -> Rob Turn -> Rob Turn -> Sacrifice -> Sacrifice.
Yes, two Sacrifices still kill. One Blast means they first does 70% instead of 97%, the second therefore does 35%. So I was wrong; Arnaud shouldn't use Blast after all, but instead Sleep. This gives him a 50% chance to give himself a win.
So even on the 25% chance of Rob Turn missing, Clarissa just needs to dodge Sleep and then to make four 75% shots in a row (15.8% chance). Unlikely? Sure. But if you add up 15.8% of 25% (3.9%) and add that to the 45.4% chance of winning with the first Rob Turn hitting using the initial strategy, her odds are now something like 49.3%. And there's more. If that second Rob Turn listed in the recovery strategy misses, that's okay, as long as she dodges another Sleep and Rob Turns twice + Sacrifice twice again. And so on. Baaasically, I'm pretty sure it's going to come up with over a 50% chance that Clarissa wins. Very close, though! And if someone wanted to penalise her for relying on an unreliable strategy like this (as indeed she does aganst anyone with above average HP), that's fine with me.