While the number one rule of inking is to stay faithful to the pencils, I can think of many cases where inkers “overwhelmed” the pencils, and made them better.  Eg., I loved Steve Bissette and John Totleben on Swamp Thing; once Totleben started pencilling and inking, it was clear he was the real talent of the art team.  Klaus Janson can complement a good penciller like Frank Miller or Gil Kane, or he can totally elevate a pedestrian penciller like Sal Buscema.  And there was that one issue of X-Men where Tom Palmer went all out to make Don Heck’s pencils look like Adams (and succeeded!).

Buscema's 1970's work varied based on who his inker was (he was doing a lot of work and probably did looser pencils at the time), but he was one of the best when it came to telling the story through pictures.

The comics business was a lot different in the 1960s and 70s.  Work had to be done on time and dependable artists were worth their weight in gold to the publishers.  Guys like Kirby, Heck, Tuska, Mooney and Sal Buscema were work horses, not plow horses.

Also, is the number one job of an inker to be faithful to the pencils, or to ensure that the story is being told is clearly as possible, to be printed?

And I agree, Sal Buscema is a treasure. Following Walt Simon on Thor was no mean feet, and he delivered!