Sounds like a plausible theory. Everybody start writing that shit down. I guess I'll have to start my spreadsheet over.
The problem now is that we need to figure out just how close the ilvl has to be to get certain %.
The good news is that I think T11 and T12 have the largest variance in ilvls, so getting useful data from lower level items as people level alts should be fairly easy, if people keep providing data.
For what it's worth, gold enigmatic +8 weapons are ilvl 145. The best thing you can buy on the AH are blue or gold items that are both 139 (this would make blues the same % success as golds by the way). Whites and Greens are 135.