I can't comment much on Verne, seeing as the majority of his time on top happened before I was around and watching wrestling. I have a few words at the end of this on him.
As far as a numeric comparison between Bock and Hogan, I can't really make one as I'd prefer to see the numbers to verify my own memories of them both at various points.
I would suggest that Hogan was a legit phenomena from his face turn forward and he drew big against everyone, and. in similar circumstances, would have done so in any company in North America in the years before his WWF run.
Put it this way: Super Sunday probably doesn't become a viable event to try and run if anyone but Hogan is in the challenger spot in that time period. You couldn't have positioned anyone else in wrestling at that time for that sort of challenge that I can think of, especially building to that program for an entire year before executing it.
Bock was a steadier draw over a longer period of time in the AWA. People hated Bock and Heenan so much that the idea that the latest challenger could beat him was always present and brought people into the arena. As much as the Wanz reign gets criticized, or even Jumbo winning it without any real AWA buildup, it did reinforce the idea that the title could change hands anytime and that certainly helped combined with the fan desire to see Bock and Bobby take one on the chin.
(You can't sleep on Heenan as being a big part of Bock's drawing power and I would be interested to see the numbers in terms of Bock alone after Heenan went to Georgia for an extended period vs. Bock with Heenan before and after that.)
The rebound factor after Verne retired with the title and Nick got it back I think speaks hugely for Nick's ability to draw in different ways, which one would have to do to stay relevant in a territory with limited bigger cities to work in.
His first challenger after being awarded the title in 1981 was Baron Von Raschke. Raschke was the hottest face in the AWA in June of 1981, in the role of Mad Dog's avenger vs. Blackwell and Studd, but as a title challenger he did not translate well. Nobody bought Baron being able to carry the title, especially a month after the title went back to Nick. Their one Minneapolis bout on 6/19 drew poorly and their series was a one-and-done. Had they drawn I believe they would have stuck with that program as per the usual AWA title programs of the time frame.
Kaissie had just come in and was getting over very nicely as a psycho heel (the sword angle vs. Tito on TV was intense), so matching him up vs. Nick heel vs. heel was programmed...risky to be sure, but Nick's ability to play the lesser of two evils in that scenario was good enough to draw for several months vs. Kaissie in the Twin Cities.
Not everyone could make that transition and then go right back to being the guy everyone paid to see get beaten, and Bockwinkel literally did a good enough job to re-elevate his status as Champ back to pre-Verne retirement angle status.
Hogan the Phenom drew great numbers. Bock was steadier and had to be programmed more creatively to maintain his levels.
As for Verne, I can tell you that his celebrity in Minnesota was enough to stay on top of his own promotion for decades and draw well enough for the AWA to be a big deal, and to stay a big deal for decades. There is no way that would have happened if he wasn't a draw and a money magnet in the little wrestling world he created.
Probably not exactly what you were looking for, but when I get rolling on AWA stuff I tend to babble.