My conclusion is there is never a valid reason to deny a Main Spec best in slot /roll. It is incompatible with a clean "Right to Roll" system. Losing a critical upgrade to a trivial itemization change is a slap in the face, being denied a roll on your Best in Slot is getting stabbed in the back. I am back to relying on the nature of random: Everything Happens. This includes some painful pitfalls, but everyone number will come up.