Rick, I agree 100 percent with you about Colan. I preferred him on horror, too. That's where the shadowy qualities of his style worked best. On superheroes, they could seem intrusive.
Regarding some of the other artists you mentioned:
Wally Wood on JSA was genius, especially when they were in Camelot and then in that weird futuristic world.
John Byrne, nothing he says can make me stop loving his X-Men, or his Alpha Flight, or the first 3 years of his Fantastic Four.
Dick Dillin -- I'm smiling as I type this. It always makes me happy to learn someone else is a fan of his. He genuinely seemed to enjoy the challenges the JLA gig brought with it, especially on the Annual team ups with the JSA. Nothing against George PĂ©rez, but I wish Dillin had lived long enough to draw the entire JLA/JSA/New Gods team up.
Jan Duursema, I agree on Arion, very underrated run on an underrated character. Her work on the last year or so of Hawkworld almost redeemed the aspects of that series that I disliked.
Leonard Kirk, along with Supergirl and JSA, also drew a sizable portion of Peter David's long-form X-Factor run, which is worth checking out whenever Marvel finally gets around to collecting it in the Omnibus format.