“It hadn’t even lost a third of its HP” Meaning the Army has was woefully underpeowered.
No, all it means it that the army dealt from 0-32.99% of the boss' HP by the time he walked in. Later we see that they continued to fight on.
Asuna’s attacks were described as “imperceptible”
It was described as "nearly imperceptible", and that was for one strike. Your minor deceptions are noted. There is also the naive implication that if you aren't doing big damage to a certain opponent, then you aren't one of the best fighters.
All while Kirito tanked it solo.
Except for all the cases where he didn't tank it. Immediately after the almost imperceptible strike, for example, we see asuna dodging a blow. You then go on to say that Klein's and Asuna's tanking wasn't effective because they weren't doing much damage. In case you didn't know, a tank should take or avoid hits, and dealing damage is secondary.
You are playing word games again. He tanked it until he wasn't tanking it anymore. With your same scheme, we could say that Asuna tanked it solo until she wasn't tanking it solo, and that Klein was tanking it solo until he wasn't tanking anymore. Everyone tanked it solo! Such fun we have if we are playing wordgames!
Let's look at Asuna's contributions a bit more:
Her sword left white tracers behind as it flew forward and collided with the Gleameyes’s blade, sparks flying in every direction. Both of them were knocked backward by the force of the impact, leaving a space in between. “Switch!” I leaped in to face the enemy without missing a beat. The demon recovered from its momentary paralysis and swung hard.
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Klein’s guild we’re picking up bodies and not in the fight. “Klein’s party lifting up fallen army soldiers to drag them out of the room"
At one point, but assuming they were all carrying soldiers all the time is just that, an assumption. We know for certain that Klein was fighting the monster. He "filled in with his Katana just in time".
And Gleming eyes still having the majority of his
Another assumption. Kirito says it's the first time he actually saw the hp decrease, but we know that other people have damaged the monster before this, and that actual damage in this case means big damage.
All the while, you should know that in the chaos of the fight, Kirito doesn't notice everything that is happening, it was even described that he could barely see the enemy, and that something not being described does not mean that it did not happen.
Despite the heroics and contributions of all the people involved, Kirito only barely survived with a sliver of health. I wouldn't call that as almost soloing personally, but you are free to use the vague judgement however you wish.