Guys, this might be late into the discussion already, but I don't think Ubo made a newbie mistake, I think he was led towards making a mistake. When Kurapica mentions he makes it seem like he's a manipulator, that implies no Gyo will be needed as the chain is a real one being manipulated, and all Nen will be required to deal with it. In other words, what you get is what you see, so why bother with In? It's not like a manipulator will throw Nen bullets or conjure anything, it's not their ability.
Whenever Kurapica convinced Ubo he was a manipulator, that's when he won that fight. Otherwise Ubo would have noticed the chain in In and all his plans would have gone down the drain. It was a necessary part of the plan in order to trick Ubo into overlooking In.
That's the official explanation which make sense until you realize every Emission technique can be hidden by In as well.
If people aren't used dealing with In, you'd literally die the first time you face against anyone who has decent Emission attacks that knows how to use In. It'd be common to see random guys have their face blown off by Emission + In combos. So if you managed to survive even a couple of to-the-death battle, you should have Gyo on permanently just to deal with Emission. By the way, Manipulate is only one school away from Emission. Pufu is shown to be capable of using very powerful aura blast attacks. So even though everything Kurapika said about pretending to Manipulate make sense, it wouldn't have mattered because anyone who managed to survive even one fight in HXH would've realized you got to know how to deal with In or you'd immediately die to any Emission techniques.
Ubogin's problem is because he was the last guy who participated in a fight before In got phased out as a valid tactic.
---------- Post added at 07:52 PM ---------- Previous post was at 07:38 PM ----------
Pakunoda was a non fighting member of the ryodan, I don't think that really was a newbie mistake. Its not like gon did not break illumi's arm before too (illumi certainly did not use nen though). I don't think the ryodan not being flawless in their actions means they made newby mistakes.
Also, what does their reaction when the lights went off have to do with anything? Its not like they were actually attacked and taken down. They had physics against them (their eyes one way or another needed a second to get used to the dark) and kurapika's chain would have neutralized all nen. And zetsu is supposed to fool people, there is not reason for it otherwise. Gon and killua should be considered pros at that much at least, heck, gon was able to fool hisoka without even using zetsu (and the guy is able to detect the presence of someone under a perfect zetsu).
Zetsu is comparable to being really sneaky, just like having extremely good perception is comparable to using En (Hisoka detected Kalluto using Zetsu with just his senses alone).
As an aside, Machi's defense in the dark shows a lot of skill. She guarded her head because that's more vulnerable than say, her heart, which is protected by a layer of muscle. Although the Spiders may be battle-tested, there's no reason why they shouldn't panic for at least a moment when they're basically completely blinded. I see no reason why they'd be imprevious to attacks from Gon or Killua at that point, and the fact that they only broke a few ribs while totally surprised should be viewed as a plus, not a minus.
Kurapika estimated that it takes at least 1 second for the Spiders to get used to the darkness, and that's actually a very long time in HXH so it's reasonable to expect them to take significant damage in this period.
