i could be a factor of things. If you are typing into field1 then you will have to click off or lose focus on that field for the control to work. If you are doing that, I would put a rule that says if Field1 is blank...disable drop down.
also try adding another rule that says user role is not equal to production....disable drop down. leave the original rule also. That should help. But in theory what you have should work fine.
Also check on the lower right hand corner for what role the user is actually viewing the form as. Roles in infopath could be a robust tool, but lack in some reguards. For example overlapping users in both user groups. They are read top down when assigning the role the current user gets.