I agree Lindsay's numbers need to be discounted somewhat since he played so much with Howe, but the question is how much.
Argument against him - his scoring plummeted in 1958, once he was traded to Chicago (punishment for trying to organize a players' union). Chicago was a bad team (lowest scoring team in the NHL) but he went from 85 points (2nd in the league) to 39 points (out of the top 30), in roughly the same number of games played.
And, just to paint a somewhat greyer picture :
Counter-argument 1 : He rebounded (a bit) in 1959.
Counter-argument 2 : He wasn't a spring chicken anymore, and Lindsay hitting a wall at some point was probably expected (I know it goes a bit against counter-argument 1). I'd also add that he was an "old" 32 years old man (that's a really weird thing to say). By then, he had more or less 11 full seasons (and a partial season in 54-55 when he missed roughy 20 games). That might not seem like a lot, but, unless I got my numbers wrong, he was #3rd in career RS games played (and 2nd in career games played) by 57-58. On top of that, he never missed the playoffs, meaning that, by 57-58, he had already played 116 playoffs games. Someone can correct me if I'm wrong, but I think he was, at that time, the all-time leader in playoffs games played (the one player that I suspected had more is Émile Bouchard, and he had "only" 114). And, while this doesn't do much in the grand scheme of things, but Lindsay wasn't a big man, as opposed to Emile Bouchard and Dit Clapper and even Maurice Richard (to a lesser extent), and he played a big man's game, so there are reasons to be believe he might have been somewhat legitmately damaged by then.
Counter-argument 3 : There are absolutely reasons to believe Howe contributed quite a bit to Ted Lindsay's production in 56-57. But that was a VERY productive season for Lindsay (2nd in points, leads league in assists. Even if cutting down his production by 25%, which is a totally random number that I just made up to make the calculating easier, he'd still end up with 64 points, which would put him 5th in scoring that season. .. It would still be a great season.
Counter-argument 4 : More importantly, 56-57 is only one season, what would be Lindsay's last prime season. He already had 8 full seasons of playing at elite level (prime season), one partial season (during his prime), one other when he led his team at ES scoring at 21 years old and his "formative" years.