I agree with what you say about Jok. So far in his career he has not shown much of an ability to attack off the dribble.
However, I don't think I would have described White as a true scorer before his senior year. Most of his points in his career came from alley-oops, fast breaks, or garbage points off offensive rebounds. He wasn't a good outside shooter, and he did not have very good handles. He did have an ability to get to the free throw line, as you mentioned, and that is how he did nearly half of his damage his senior year.
Jok is averaging more points per game as junior than White did as a junior, and I don't see why it is unreasonable to say that Jok will average more as a senior than White did as a senior. While Jok hasn't shown the ability to drive to the bucket, he still has an extremely quick release and can get his perimeter shot off in tight spaces, and that includes off the dribble. I don't expect Jok to suddenly be able to create a lot of space off the dribble, but with his shot he doesn't need much space, and I think the volume of his shots will increase next year which will result in him scoring 16+ points per game.
The real question for Jok next year will be how efficiently he can score. It's easy to score more when you take more shots, but if he isn't efficient with his scoring next year then this team could be in trouble, unless one of the younger players is better than expected.
Looking at the roster next year, I think there is only one player we can say is truly an above-average Big 10 player and that is Jok. Uhl and Baer should be considered at least average Big 10 players, and next year I think they could be above average. Still, in order to be in the top half of the Big 10 we will need big contributions from unproven players. I do believe there is a lot of talent in guys like Williams, Fleming, Moss, Hutton, Wagner, and Cook, but those players are still unproven and to expect any of them to be better than average Big 10 players is too much to ask for.
If everything goes right, I could see next year's team being top 25-caliber. I could also see them winning just 6 Big 10 games. It's a crapshoot, and my best guess is that they will be a weak bubble team destined for the NIT.