Agreed on the rear wheel tracking being the likely culprit. The thrust angle is the first thing any tracking session must check. This is adjusted through the rear wheel toe settings. That done, the fronts are then set against the rears. This prevents 'crabbing' and the sort of front tyre wear you describe.
EDIT: This diagram shows how the rears control front tyre wear by forcing the car to crab off-line.
These rear toes put the thrust angle out of spec.
TC