Exactly! You don't see the former. In the difficult content, you only see the players that want to be there, and challenge is only one of several incentives. Me playing with friends is just one example. The point being skilled players, capable of performing in high-end duties can be found everywhere, so what the OP is trying to use to evaluate player skill isn't going to work. Many do wish to put their skills to the test. But on the contrary, said players may not have a desire to express this skill because their passion lies elsewhere. However I will agree to a player who feels capable, will at the very least have a desire to try the content even if they don't actually go into it. This could be for multiple reasons.
Mindset/psyche is indeed a strong descriptor, but not a full tell tale indicator of skill level. So there are indeed issues. It can definitely contribute to a player performing very well in a duty, and then performing poorly in the exact same duty the next time they go in; or doing poorly in a simple duty, and extremely well in a more difficult one. Adding to the difficulty of determining player skill is the fact that this is a multi-player game, so not only is there an individual stat, but also this player's ability to work and coordinate with others.
