I feel part of the reason we see variance among rankings is that some lean towards ceiling in their evaluations, and some lean towards performance to-date. (Of course other factors, age, league, etc.)
Just sticking to what you've said here, I have no idea (since I haven't seen him directly) if I'd consider him more on-par with Westburg and Stowers or Rom and Vavra in-terms of actual ability.
I can agree, that a Rom / Vavra level prospect seems to be what his perceived value was based looking at the cumulative 3rd party rankings across the board. But we have seen an outlier, which is more in-line with Westburg and Stowers. Maybe the outlier is wrong, and the consensus is right. Maybe he has more ceiling than has generally been recognized.
If he performs this year, and his perception goes up... that points to the idea his quality was under recognized by the consensus.
For me.... I wouldn't have Henderson in my rankings, as I feel he graduated.
I'd also have him above Johnson, and maybe Fabian. So, I'd have him 11th or 12th... and with the assumption that Grayson makes the ML rotation, and Hall either joins the ML team out of camp, or shortly thereafter... for me, he's basically the best pitching prospect currently in the system.
It will be interesting to see what he does this year, and if the O's scouts were right about their evaluation.