Sorry but he hasn't.
Adrian Peterson in 2012 had a 458 DYAR.
Bell is a better 2 way back than Peterson, that's for sure. But it's also worth note that Bell has a much better QB than Peterson ever has. Pittsburgh has many other threats that can hurt you (Brown is one of the best WRs in the NFL, Roethlsberger's Mobility, their defense)
In 2012 Peterson carried Minnesota on his back. Minnesota had no business being in the playoffs. Christian Ponder was their QB. PErcy "Migraine" Harvin was their top receiver, their defense was comfortably below average sporting a good run defense but one of the lower pass defenses in the league. Overall they had no business being in the playoffs with the 9th highest total team efficiency. But because of Adrian Peterson they were. While more efficient teams like the Giants, Panthers, and Bears were left on the outside looking in, Peterson carried them to the playoffs on his back.
How is a team with the 9th highest total efficiency having no business in the playoffs? There are 12 playoff teams. Could they have been lucky? Sure, they had a +10 TO margin. AP had a great season. What Leveon Bell is putting up this season is historic.