Okay, some good news (well not really news, more like info) about Jokiharju. Using this
site, Jokiharju would be expected to score around 27pts next year if he played in the NHL. If you put in the info for Sergachev's conversion rate before he made the jump, his points were expected to be around 22. If you did McAvoy, that number would be 21.
So Jokiharju, one year after his draft, would statistically have a better chance of putting up more points in his rookie NHL season than Sergachev or McAvoy had at that same point (draft +1 year).
Both of those guys ended up being around .5ppg in their rookie seasons this year, and it'll be hard for HJ to do the same, but it's obvious that he has the ability.