While chunk plays are important, yards also matter unless you have a top 5 D....
Y/A and ANY/A both have strong correlation to winning... JB is 20th and 28th in those two categories. He was close to last in air yards (29th) as well, and 26th in deep attempts. Also, JB wasn't really hitting big "called" or "scripted" plays early. Many of his longer completions were on broken plays. That's nice and all, but it's not something that can be relied upon consistently.
Improve the pass rush, and it's a lot easier on everyone in coverage.
I doubt they move Oke away from starting SAM, and you really don't want him playing in the middle on early downs. Willis is great in the box, but got exploited vs the pass (allowed 27 catches on 31 targets). Guessing you'll see him get the majority of snaps vs run heavy teams and early downs, and less vs pass happy teams and later downs.
Aiyuk will likely go somewhere between 2nd and 4th based on the mocks I've seen. Not sure I would use that kind of draft pick on someone to be just a returner and gunner. I think he's got high upside, so would expect most teams to look at him as a WR2 or 3 at slot, or perhaps even a 1 at Z. If he improves vs the press and gets better at attacking the ball, he could be really really good. As a fan of Herm, I watched a decent amount of ASU, and the kid can play (if used properly)
At returner, I'm very happy with how Hines did at PR. Also liked what I saw from Dulin at KR (only a few opportunities). Pascal also had pretty good numbers at KR. Keep in mind we ended up #1 in the NFL in PR AVG, and #13 in KR AVG, so not really a huge need. The only thing I want to see change a bit is the willingness to return (instead of touch back or fair catch), and that's likely coaching, not player. I'm always happy to improve if we have someone on the roster that's better though, just not sure I'd draft a guy in an attempt to improve returns.