It might be useful to add a drop down field "Difficulty" for questions. With a very limited set of options, say:
This way, users could easily judge if they can answer a specific question (depending on their experience in the topic) and how much time it will probably take.
Beginners usually know they are new so they can easily select Beginner. Those with some experience just select Advanced and those working on a topic for years may chose Expert. I think it's not very difficult to judge halfway correctly.
And the difficulty rating does not have to be very precise anyway, it's more a rough estimate by the asking person.
As an addition, rep gained on this topic can be multiplied with a difficulty factor. This would solve the problem of lots of rep for often-viewed and easy to answer questions and few rep for less-viewed, difficult questions.
Thank you so far for the answers. I clearly underestimated the fact that some users are going to always chose Expert difficulty.
Maybe readers voting on the difficulty would be a workaround. Of course, we cannot use the rep factor then, for the same reason.
This kind of voting would obviously introduce a whole new set of issues, since we could vote on both content and difficulty (I'm almost positive this kind of proposal existed before?).