1)
"Would disagree here. There's no indication of an explicit attempt, so not valid to say that she 'failed'. Miria phantom-dodged T2 and then crossed swords with her."
Yes, there's no indication. And yes, word "fail" may not have been the best to use. Let me reiterate. Miria, despite having a good clue how one twin can fight in an awakened form (seeing them switch but never two of them fighting in such form at the same time) did not target the T2 after escaping from T1A. So unless she knew that she would risk the other awakening for good (although seeing how fast they were in switching and de-awakening the chances of that were rather slim) it would just mean she wasn't fast enough to do it.
"Would disagree. She dodged the first attack by T1A, but T2 took advantage of Miria's airtime to position herself to where she could attack before Miria could move away. The "ku" was annoyance at the cooperative advantage T2 got due to the dodge."
Would disagree. It would be hard for Yagi to write
"ku" while having Miria's back in the picture and she said
ku just after T1A attacked. Also, T1A should be much faster than T1 not using youki and Miria managed only - with difficulty which
ku suggests - to dodge T1A and couldn't position herself so that she wouldn't be vulnerable to attack performed by T2. So T1A was enough to make her struggle. She couldn't do a THING to T1A and couldn't do a thing to 0% youki T2 when she attacked Miria using her being cornered by her sister. At this time she was attacked by 0% T2 and she didn't use this chance to incapacitate her because she just couldn't. She wasn't prepared and properly positioned to do it and wasn't fast enough to change it
all of this because of T1A.
"T1A reverts to T1 while T2 makes the attack against falling Miria. T2 continues the attack, and, since T1 is no longer awakened, is able to draw on her own power to make a 'surprise' attack, which Miria dodged. T2A presses the attack, positioning Miria so that T1 can attack from behind."
Which was possible only because their attacks were too slow. Miria could barely manage to dodge T1A attacks but she could do it, so it's no wonder she could dodge attacks performed by unawakened twins. Yes, there were two of them fighting combined but the same situation was earlier. Instead of pushing Miria to the limit by attacking with T1A + T2 combination they've powered down. I don't see how that could add element of surprise to their attacks by doing that. They were not cloaked even at 0% youki. Maybe she would make less noise and wouldn't cast such a big shadow (although Miria might not have noticed it if T1A would be "on the right side of the sun") but that's irrelevant when taking into account much higher speed and power advantage (and attack range). It would be obvious to Miria that the other twin was somewhere close and would attack and she was on her guard and knew from which directions she was likely to be attacked (of course from the directions she wouldn't be able to spot) and ultimately everything came down to speed difference.
"Yes, the raw power of the attack is 'weaker' (possibly; conceivably each individual attack was just as strong since each used the awakened form; cf: Quick Sword). However the point was not pure strength, but tactical advantage. Pin Miria down in a desperate defense to allow the other twin to make an unobserved attack from the rear. Excellent use of tactics. "
And they couldn't have use the same tactic in a T1A + T2 scenario? How come? Besides being faster the other twin would also have a wider range of attacks so it would be additionally more difficult to dodge. Don't forget that Miria was on a defensive this whole time and she was being cornered just by 30% T2 (or maybe more than 30% seeing her awakened tentacles)! And you're most probably wrong by saying it was as QS. In QS you store ALL your youki in your arm, we don't have any indication it was the case in their case (awakened beings have their youki spread out, they do not enhance particular parts of the body at the cost of other parts at their will AFAWK). They were using their awakened limbs but the rest of their bodies were unawakened so they weren't as fast or as strong or as armored, it was only a fraction of their awakened powers.
3)
"While it's definitely tiring, saying that "the fight exhausted her" is a bit of an overstatement. Even Rubel's statement is that exhaustion is "beginning to set in". One must also consider that, even if they weren't especially challenging, she has had to work her way through ~30 other Claymores already before this point."
Let's be honest here, Miria could have insta-KOed 27 out of these 30 Claymores with one phantom. And as far as Miria knew she could have performed her phantom as many times as she wanted (we know it thanks to Deneve who most likely knew about new phantom from Miria herself when she told Helen about it). Obviously Miria did not feel a thing at this point and while it may have shortened her number of mirages she could perform before starting to leak youki by 1 or 2 mirages it was insignificant when compared to the strain she had to endure while fighting twins. Clearly they were making her use her new phantom to the limit and at some point to keep her speed she had to leak youki. Maybe if she didn't go to the absolute speed limit of her new mirage she could really do her phantoms many, many times but with them Miria couldn't go half-assed. And yet she said
"I could easily chop their heads off" which is the main thing I have problem with and with which I disagree seeing her performance.
"They aren't sweating after their fight with Roxanne either. Just bleeding a lot. Their complete blankness when fighting makes me think that you wouldn't notice exhaustion in them until they were just about ready to fall over dead."
Actually we also see "haa, haa, haa" from them which suggests exhaustion. Earlier we don't see that because it was the start of the fight and because we haven't seen much of a fight (more like not at all). In short, if anything it confirms that Miria was a much easier opponent to them and it certainly does not in any way suggest they just don't show exhaustion. What matters the most however is that while we could see signs of exhaustion (so to not overstate) on Miria's face we don't see anything like it on twins' faces.
"Debatable that they slowed down. But I'd argue that it should be trivial for her to cut off their heads regardless. Any time she's used her phantom, it was always to move some significant distance away. It would have been easy to instead cut their heads off at those points."
In that case I wouldn't see how her phantom would be worse than Hysteria's elegant attack. Also I would wonder why would it be more difficult to target their necks or stomachs with a blunt side of the sword to make them unconscious (similar to what Deneve did in Riful encounter). I think the main problem of Miria that her phantom is used mainly as a defensive measure is
because while she has super fast legs she doesn't have super fast swings and she certainly does not have as fast swings as Hysteria and doesn't have enough overall power to match her leg's speed, hence she can't perform such precise attacks. So when she would try to chop their heads off while doing her phantom it would either be countered since she wouldn't have swing fast enough or she wouldn't be able to hit their necks since at the moment she would start the cut she would be 10 m away the next moment and would only manage to make a shallow, easily closed wound.
4) I'll admit she was surprised and dismayed but you haven't commented my main point -
she cut an arm of a 0% T1. So while I could admit that Miria would be able to defeat/kill 0% twins I doubt she could do it if they were more serious. You also seem to use an excuse of Miria being dismayed for her being on a defensive which I disagree with. She couldn't have a better chance to deal with the twins than when one had no arm and the other had no backup and she failed to do it because IMO the other twin did not let her because T2 was too fast at 30%.
"Miria however was basically fighting as if she had 30% youki released 7 years ago (otherwise she couldn't do her phantom, at least not until Pieta).So the difference is huge and shows that what Miria did was nothing."
Let me try to explain what I meant by that and correct me if I'm wrong. Basically I meant that Miria defeating 0% T1 while she herself was using 30% youki was nothing special. After half-awakening she had almost the same speed and power of phantom as 7 years ago in Slasher's arc when she had to use 30% youki. We know thanks to Deneve that half-awakening allows to increase youki they can use at normal times (literally she said: "My first youriki release in 7 years seems to be increasing my youki almost to the limit even during normal times"), i.e. they have more access to it while not releasing it externally. But they are using huge amounts of it as Claymores, it just doesn't show. That's a huge advantage. To be able to use 80% youki and not awaken. They don't have to awaken any more to have huge power boost. And Miria has that access to her hidden power. You may disagree here but that was the point I was making relevant to Miria vs. twins discussion since it would show (assuming I'm right) that Miria wasn't fighting them at 0% but she was using more youki, it just couldn't be detected. So it's not like Miria would have be much more powerful if she would release 30% youki (at least not in leg speed). Although after seeing 116th chapter this argument has become weaker and has made Miria a retard at the same time (by not releasing youki when fighting Riguald or twins).
I've written sth more about this here.
5)
"Every step further you move back is another step you have to move forward in order to attack again, which does nothing but slow you down."
Sure, but the opponent is also moving towards you, and not one but two of them. So in this case I would think that side-stepping or backing away that one step further would be more safe since the opponent would nevertheless be close. Miria would always be closer to one of them than the other and could attack that one. Plus if she would actually be able to make a bigger dodging move she should also be able to make an attack move this much closer.
6) Yes, she did not intend to cut their heads off but she said it would be
EASY to cut their heads and that's the problem I've been arguing from the start. It was NOT easy to her since she couldn't have incapacitated them even when she was being serious and was going as much as she could without releasing youki. And since she couldn't do a slightly more difficult thing to even one of them (and in 0% mode, not 30% or awakened !!!) I don't see how she could EASILY cut heads of both of them.
7) Possible maybe, but not too good argument IMO. After all, at this point she had already defeated all Claymores and twins were the only ones left (as far as she knew). So seeing that she could "easily cut their heads off" if she released youki they shouldn't even have time to think that she intends to "seriously kill them". Besides, you're indirectly admitting here that twins must have known Miria didn't want to kill them, which would further explain why they also weren't serious and didn't fight in a T1A+T2 combination the whole time.
8) I pretty much agree with everything you said here.
"Of course the primary argument was about the status of Miria relative to a standard #1 Claymore, and none of this convinces me of it being any more or less likely."
Actually, what I was trying to argue here primarily was that Miria, contrary to what she thought, COULD NOT cut the twins' heads easily. I agree she's a strong #2 but the way I see it she would never have #1 position unless there would be warriors of lower class than the shrimp twins.
