His career is similar to Markus Naslund but IMO even slightly worse and Naslund isn't a HOF'er.
Naslund like Benn had an incredible 3-year peak (Benn has a Ross but Naslund was leading the league until the final day of the season and won the Pearson so pretty equal seasons).
Difference is Naslund had a legitimate claim for top 5 player in the world for a 3-year stretch and Benn was never top 15 even with the Ross.
A cup wouldn't be enough for Benn in any case but especially since he would most likely be a passenger on a Dallas cup-winning team this season.
Off hand, I would assume Robertson, HIntz, Heiskanen, Johnston, Duchene, Seguin, Stankoven, and of course Oettinger would be bigger factors in any success than Benn.
Benn was a top 5 or 6 player in the league from 2014 to 2016
2014 - He made the 1st NHL team and was top 5 to 7 player in the league (Crosby, Malkin, Getzlaf, Seguin, Giroux)
2015 - Won the ross, made the 2nd NHL team and was 5th to 7 th best in the league (Price, OV, Crosby, Tavares, Kane, Datsyuk)
2016 - Made 1st NHL team and was 3rd or 4th best player in the league being top 3 in hart (Kane, Karlsson, Crosby, Mcdavid, Holtby)
He isn't a hall of famer but he was very good in his 3-year peak, being similar to Panarin or Pastranak or Rantanen level player from 2014-2016