Here, I did some quick Art Ross research while siting in my car in my laptop, leeching off someone's wireless network while waiting for my dog to get groomed.
I think if you're only going as deep as 5th, it's only fair that with Ross we concern ourselves with the times he was in the top-3 in his league among defensemen, since it was essentially a half league. I will do my best to account for other star players' stints at defense and forward where possible. I will also only include the 1907 season and onwards, because that was when he began playing in a "top" league.
1907 - Ross was in a 3-way tie for 2nd behind Hugh Ross, with Si Griffis and Paddy Chambers. Joe Hall had many more points but I know Hall was a forward at this time.
1908 - It appears Ross was in a tie for 2nd, again, with Frank Patrick. Moose Johnson topped them by one goal. Was Johnson a forward at the time? I forget. Hall topped them but he was still a forward.
1911 - Ross' 6 points were actually tied for the most in the NHA by a defenseman that season, and he did it in fewer games. Taylor outscored him but as a rover - not sure if you count that.
1912 - Ross topped the NHA. Hall and Cleghorn were 2nd and 3rd. This was Ross' peak.
1913 - Ross again topped the NHA, with Cleghorn, McNamara, Cameron and Hall within 4 points of him.
1916 - Ross finished 2nd, a point behind McNamara and three ahead of Foghorn.
I think it's fair to say that if you're top-3 in the NHA at this time, you're top 5 in all of hockey. If I was to speculate what this translates out to in a consolidated league, I'd say:
1, 1, 2, 3, 4, 5. Gonchar territory, or a little better.
Not campaigning for anyone here, I just like to research and post what I find