Kurenai, Shino & Hinata VS Karin & Suigestu

[Nattana]

No, it's not logic that applies here because Genjutsu and a Maze obviously aren't the same thing.

And no, those are terrible examples because those aren't Kurenai's Genjutsu. They are Genjutsu that are stronger and/or work differently. Kurenai's Genjutsu in particular can be broken with pain as she herself has shown.

She didn't use pain. Her lip wasn't bleeding outside the genjutsu, and besides how would they know to counter it that way? Sure karin can break out but suigetsu?

Well I've never noticed that until now. So the lip bite method is debunked now, since as seen in Kiba's example, his finger had to be broken in reality by some external source (his shadows) and not only inside Genjutsu.