The NFL is comparatively soft on suspending athletes for PEDs. In baseball, Robinson Cano of the Mets was suspended for a full season. In hockey, Nate Schmidt was suspended for 20 games. In the NBA, Wilson Chandler of the Brooklyn Nets was suspended for 25 games. In Australia, a rugby league player, Bronson Xerri received a 4 year suspension. In swimming, Ryan Lochte received a 14 month suspension. In cycling, Lance Armstrong received a lifetime ban for PEDs.
Fuller and Robey are actually very lucky to just get 6 games suspensions. If the NFL was really serious about addressing the problem, they would suspend them for at least a year.