As Jenn said, how I do my sketches for drawings depends on the project. In the case of the above illustrations, I had a slew of spot drawings in line and wash to do in a short amount of time. So these have to be done quickly, with not too much time spent on the sektches. But because I do a lot of magazine spreads, posters, etc., (on which I spend a lot of time working on the roughs/sketches), I'll get bogged down in working out too much detail in these smaller, should-be-simpler, sketches. The above looks like just that. The sketch is fairly tight and detailed.
I don't know how others do sketches like this. If it's too loose, the AD might not be able to get a good idea of how the end illustration will look. But if it's too detailed, one can end up spending way too much time on something if there ends up being a lot of changes, and no room for flexibility if you decide to change some things. Tough line to walk.