Terry was 14th in yards in '82, a strike-shortened season. But plenty of QBs could be considered as good/better than he was. Some guys like Dan Fouts. Joe Montana, Kenny Anderson, Danny White, Ron Jaworski, Jim Plunkett and Joe Theismann were in the mix. I think more of a reason they didn't draft Marino had to do with the fact that they used a 1st-round pick on Mark Malone in 1980.
There was nothing to indicate Malone wasn't going to be a stellar QB by the '83 draft. Of course, he wasn't, but they couldn't have known by then without any game play to evaluate him on. Malone was the "ultimate athlete" coming out in 1980.
And as you mentioned, "Who really knew with Bradshaw?" with his injury.