I'd disagree with you on Federko, I remember him being in the perennial top 20 scorers in the 80s, he and Joe Mullen were a reason for the Blues being somewhat competitive. He's also an over 1000 pt scorer who averaged pt. per game in regular season and playoffs. Most of those guys are in the Hall. Fleury is not, but he hardly had any playoff appearances or success, on bad Calgary teams as the 90s wore on. Guys like Steve Larmer and Brian Propp are close in that regards, but overlooked for their very stellar careers on non dynasty teams. Maybe the one that irks me the most is Bobby Smith, who sits 25th all time on the playoff scoring list, tied with Bossy, Howe and MacInnis, 4 time Stanley Cup finalist, twice with the Canadiens, twice with the North Stars. Cup winner in 1986.
I'm a little surprised that Patrik Elias has gone under the radar too, playing a key role to the Devils success. I'd have him ahead of Mogilny, though Mogilny had the much flashier start to his career.