Well, I like the misprints device, especially if done well. As it was, here, IMO. Shackleton's clues abounded in wit and indeed the wit element was enhanced by the misprints.
On the other hand I have never understood why some people get so excited by Letters latent clues, or indeed any clue where the wordplay leads to a different form of the answer (usually a non-word) to the definition. They all have merit in their own way but to me are much less satisfactory.
Still, everyone has their own likes and dislikes.
I don't think there is a link between the standard of the puzzle and number of obscurities. The problem isn't how to be difficult, it's how to work in extra information Misprints, extra words, etc are an obvious way of doing this. Sabre once did it brilliantly by hiding further instructions in the grid, and no doubt there othjer ingenious ways of doing this, but it all boils down to having a message that needs to be conveyed in some way.