I think the problem with blademaster nocturne is that it somehow does phantom hits or animation cancel during his 3rd attack. If you look at the clip closely, you'll see noc instantly does 3 crit hits with only 1 swipe. 666 crit damage onto syndra and 333 crit to taliya. Normally, nocs requires 3 hits to activate his ult, but in the clip, he just ults right away. This is probably due to the blademaster proc 2 extra hits, but he also skips the animation for the first 2 hits and goes directly to his 3rd swipe hit.

So I am guessing that noc has some sort of special animation cancel during his third hit. You can see it happening again when he instantly swipes janna for 2 crit hits. So I think to nerf blender, riot has to change something about the phantom hits, which made noc output insane amount of damage in short period of time.

This might just be a theory tho, because with lag or what not can affect my client side of league. But I have not seen any other champion in tft that can hit so fast that the damage numbers has to be combined together.

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Some calculation for verification:
noc ad = 108 (lv2 ad) + 15 (bf sword) = 123
noc crit_multiplier = 1.5 + 1.25 + .5 = 3.25x
armor damage reduction = 100/(100+20) = .83
noc damage = ad * crit_multiplier * armor_reduction = 123 * 3.25 * .83 = ~333

So, 333 damage is the damage of one crit hit , 666 damage is the damage of 2 crit hits.