I came here to say Glenn Anderson, but, as someone said above, he actually led the 1990-91 Leafs in scoring, which is bizarre.
Then, I thought maybe Brendan Shanahan, but no -- he actually led three different franchises in scoring (St.Louis, Hartford, Detroit)!
But I've got one!! Alex Delvecchio. Scored 1281 points (currently 35th, all-time) but never led the Wings in scoring, riding shotgun alongside Howe all those years. He was a remarkable player with Howe-like longevity, and he played two more seasons after Howe retired from Detroit... but then he was usurped by the new-breed, notably Marcel Dionne and Mickey Redmond. So, he never led the Wings in scoring despite finishing top-3 countless times.
Correct me if I'm wrong, but I believe Al MacInnis is another one.