Mario and Orr are not question marks they are top 4 players all time beyond debate as to where in the top 4 they fall.
Hasek - Ditto. He is not a question mark. He dominated in Europe, The NHL, Internationally and played well into his 40's, he is still freaking playing!
Forsberg - Not really a question mark we know what he did and what he could do.
Lindros is the only one that is an actual question mark. His injury really affected his play, he only had a half dozen truly full seasons all before he might have actually been in his prime. Lindros likely IMO have been in Trottier, Clarke, Sakic, Yzerman, Lafleur territory in terms of forwards for his career if he had not had those injuries but then again we can never know for sure. Now he is a possible non HHOFer. The other 4 are surefire HHOFers without doubt.
In terms of question marks for the others it is whether Orr and Mario could have been clear #1's over Gretzky. Hasek out of the Sawchuk, Plante, Roy territory and the clear #1 of all-time. Forsberg might have been in Yzerman, Sakic, Clarke Territory all time but he is still IMO easily good enough for the HHOF.