Updated: Aug 23
In PPR I don't think Pickens can touch Diontae but in .5 PPR there's a chance.
Diontae had an ADoT of 10.6 and 1.58 Yards per route ran vs Pickens 15.6 ADoT and 1.54. The difference is obvious, Pickens runs higher value, but less often targeted routes. (Keep in mind here he played with rookie Kenny Pickett and Mitch Tribisky, neither of whom pushed the ball downfield well).
Last year Diontae scored 180.7 points in PPR. Of those points, 86 were from caught passes, leaving 94.7 points from yards (No TDs). That means 48% of his points came from catching passes.
In .5 PPR he scored 137.7, with 43 coming from his Receptions and 94.7 from yardage, leaving 69% from yardage, or 31% from receptions.
Now look at Pickens. He scored 142.5 points (tds removed for fairness, 166.5 with TDs). Of those, 52 were from caught passes. His 90.5 points from yards makes 63% of his points from targets, again reflecting his deeper routes. (If we add in TDs then Pickens has roughly 68% of his points from receptions, and although the Diontaes numbers would change too with some TDs, Pickens's deeper routes naturally have more scoring chance).
In .5 PPR Pickens scored 116.5 (with his TDs removed, otherwise 140.5). Of those, 26 were from his receptions or 23%.
Look at the differences in % of points from receptions. Pickens gets 11% MORE of his points from yardage (higher value routes).
Now we have a conundrum. What is more likely to give? Pickens running high-value routes that he's good at? Or Diontae Johnson giving up some targets in an offense packed with threats like Pat Friermuth, healthy-again Najee, and Pickens? If I had to bet, I would say that it's more likely Diontae loses targets than Pickens gets crammed onto short, low ADoT targets.
All of this means, that in .5 PPR where Diontaes targets don't inflate his score as much, his lower value routes dramatically handicap his scoring. Pickens doesn't even need to break out and he could still out-perform Diontae in .5 PPR leagues. In full PPR, Pickens needs to run more types of routes to siphon targets from Diontae.
Tl;dr Pickens > Diontae in .5 PPR with no breakout
Needs more targets to outperform in PPR