Simply looking at Robinson and Potvin respectively using their rankings in defenceman points to evaluate their production relative to their contemporaries.
Denis Potvin:
Season | Rank
73/74 | 5th
74/75 | 2nd
75/76 |
1st
76/77 | 2nd
77/78 |
1st
78/79 |
1st
79/80 | T-20th
80/81 | 2nd
81/82 | 11th
82/83 | 10th
83/84 | 3rd
84/85 | 7th
85/86 | 14th
86/87 | T-23rd
87/88 | 18th
Number of offensive titles amongst defencemen: 3
Average offensive ranking amongst defencemen: 8th (best five seasons rank:
1st)
Larry Robinson:
Season | Rank
72/73 | T-95th*
73/74 | 33rd
74/75 | 5th
75/76 | 16th
76/77 |
1st
77/78 | 5th
78/79 | 7th
79/80 | 2nd
80/81 | 25th
81/82 | 14th
82/83 | 11th
83/84 | 30th
84/85 | 22nd
85/86 | 3rd
86/87 | 13th
87/88 | T-29th
88/89 | T-46th
89/90 | T-31st
90/91 | T-59th
91/92 | T-104th
*partial rookie season - just 36 GP.
Number of offensive titles amongst defencemen: 1
Average offensive ranking amongst defencemen: 28th (best five seasons rank: 3rd)
Edit: if we add in the table already provided by matnor for Lidstrom (might as well given that we're discussing defenders likely ranked from slots 5-10) and those of Red Kelly and Chris Chelios the aforementioned rankings compare as follows.
Nicklas Lidstrom:
Season | Rank
91/92 | 9th
92/93 | 34th
93/94 | 16th
94/95 | 20th
95/96 | 6th
96/97 | 3rd
97/98 |
1st
98/99 | 2nd
99/00 |
1st
00/01 | 2nd
01/02 |
1st
02/03 | 3rd
03/04 | 22nd
05/06 |
1st
06/07 | 5th
07/08 |
1st
08/09 | 3rd
09/10 | 8th
10/11 | 2nd
Number of offensive titles amongst defencemen: 5
Average offensive ranking amongst defencemen: 7th (best five seasons rank:
1st)
Chris Chelios:
Season | Rank
83/84| T-168th*
84/85| 10th
85/86| 38th**
86/87| T-19th
87/88| 9th
88/89| 4th
89/90| 43rd
90/91| 8th
91/92| T-13th
92/93| 9th
93/94| 12th
94/95| T-5th
95/96| 4th
96/97| 8th
97/98| T-21st
98/99| 19th
99/00| T-30th
00/01| T-224th***
01/02| T-17th
02/03| T-75th
03/04| T-70th
05/06| T-148th
06/07| T-144th
07/08| T-136th
08/09| T-272nd****
09/10| T-263rd*****
*partial rookie season - just 12 GP.
**partial injured season - just 41 GP.
***partial injured season - just 24 GP.
****partial veteran season - just 28 GP.
*****partial veteran season - just 7 GP.
Number of offensive titles amongst defencemen: 0
Average offensive ranking amongst defencemen: 68th (best five seasons rank: 6th)
Leonard "Red" Kelly:
Season | Rank
47/48| 4th
48/49| 5th
49/50|
1st
50/51|
1st
51/52|
1st
52/53|
1st
53/54|
1st
54/55| 2nd
55/56| 2nd
56/57| 3rd
57/58| 3rd
58/59| 11th
59/60| 6th
Number of offensive titles amongst defencemen: 5
Average offensive ranking amongst defencemen: 3rd (best five seasons rank:
1st)
A few things jump out at me from the comparative rankings.
Firstly, Red Kelly's offensive game relative to his peers might just have been the best out of any defenceman not named Orr. He led the league in scoring by a defenceman in five straight seasons, in a period when both Bill Gadsby and Doug Harvey were at their peak strength (or close to it) as NHL defenders. That is insanely impressive in a historical context. The fact that Kelly only has one season out of the top ten while playing defence, and it was an eleventh place finish no less, is also extremely impressive to his cause. His 1960 season split between Detroit and Toronto is the only other season in which he is even out of the top five in defenceman scoring, although I am not sure how many games he played at centre once Imlach converted him to a centre with the Leafs.
Secondly, despite the bemoaned lack of high-end historical competition, Lidstrom also has five finishes as a top defenceman point-wise, tied with Kelly for the lead on this list and better than even the vaunted Potvin, who many consider a better offensive player historically-speaking. Lidstrom accomplished two of these titles when all of Ray Bourque, Al MacInnis, Brian Leetch, Chris Pronger, Scott Stevens, and Chris Chelios were still considered stud defenders, or close to it. He received another one in the season after Ray Bourque retired and the season before Al MacInnis had one of his best years in his final full NHL season (2002-03). That seems to downplay the notion that Lidstrom has only dominated against sub-par competitors in the history of the position.
And lastly, we can see that even at his peak Chris Chelios was not as feared offensively as the other defencemen. He made his living as arguably the meanest SOB in the NHL at the time and in playing intimidating, even downright dirty defence, complete with fash-washes, cross-checks, hard hits, and clearing the front of the net to a degree that even Denis Potvin or Eddie Shore would have been proud of. However, offence was not his forte, even his 70+ point seasons, and it is demonstrative of how highly regarded his defensive game was that he was winning Norris Trophies as only the 4th (1989), 9th (1993), and 4th (1996) highest-scoring defenceman in the NHL. He also finished a close second to teammate Lidstrom in 2001-02, when Nick again led the league in defenceman scoring, in Norris Trophy voting despite being only 17th in the league amongst blueliners from an offensive standpoint.